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 $84.79   9.185%   $92.578   $92.58   $92.60   $92.60  
  Purchase #2 $154.87   13.450%   $175.7   $175.70   $175.70   $175.70  
  Purchase #3 $47.51   12.785%   $53.5842   $53.58   $53.60   $53.60  
  Purchase #4 $180.41   7.850%   $194.5722   $194.57   $194.55   $194.60  
  Purchase #5 $161.51   10.416%   $178.3329   $178.33   $178.35   $178.30  
  Purchase #6 $238.58   11.587%   $266.2243   $266.22   $266.20   $266.20  
  Purchase #7 $170.79   13.812%   $194.3795   $194.38   $194.40   $194.40  
  7 purchase totals = $1,038.46       $1,155.3711   $1,155.36   $1,155.40   $1,155.40