Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $228.92   3.143%   $236.115   $236.12   $236.10   $236.10  
  Purchase #2 $122.49   7.492%   $131.667   $131.67   $131.65   $131.70  
  Purchase #3 $240.48   8.542%   $261.0218   $261.02   $261.00   $261.00  
  Purchase #4 $24.43   11.337%   $27.1996   $27.20   $27.20   $27.20  
  Purchase #5 $187.72   12.300%   $210.8096   $210.81   $210.80   $210.80  
  Purchase #6 $169.29   10.513%   $187.0875   $187.09   $187.10   $187.10  
  Purchase #7 $86.87   6.755%   $92.7381   $92.74   $92.75   $92.70  
  7 purchase totals = $1,060.20       $1,146.6386   $1,146.65   $1,146.60   $1,146.60