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 $84.56   11.861%   $94.5897   $94.59   $94.60   $94.60  
  Purchase #2 $66.28   10.654%   $73.3415   $73.34   $73.35   $73.30  
  Purchase #3 $188.62   8.225%   $204.134   $204.13   $204.15   $204.10  
  Purchase #4 $223.73   8.562%   $242.8858   $242.89   $242.90   $242.90  
  Purchase #5 $94.38   4.447%   $98.5771   $98.58   $98.60   $98.60  
  Purchase #6 $188.75   13.578%   $214.3785   $214.38   $214.40   $214.40  
  Purchase #7 $198.25   11.120%   $220.2954   $220.30   $220.30   $220.30  
  7 purchase totals = $1,044.57       $1,148.2020   $1,148.21   $1,148.30   $1,148.20