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 $94.48   11.117%   $104.9833   $104.98   $105.00   $105.00  
  Purchase #2 $235.31   6.761%   $251.2193   $251.22   $251.20   $251.20  
  Purchase #3 $22.27   7.697%   $23.9841   $23.98   $24.00   $24.00  
  Purchase #4 $185.51   8.455%   $201.1949   $201.19   $201.20   $201.20  
  Purchase #5 $92.93   3.255%   $95.9549   $95.95   $95.95   $96.00  
  Purchase #6 $232.36   7.624%   $250.0751   $250.08   $250.10   $250.10  
  Purchase #7 $75.77   8.850%   $82.4756   $82.48   $82.50   $82.50  
  7 purchase totals = $938.63       $1,009.8872   $1,009.88   $1,009.95   $1,010.00