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 $141.28   7.752%   $152.232   $152.23   $152.25   $152.20  
  Purchase #2 $22.68   4.523%   $23.7058   $23.71   $23.70   $23.70  
  Purchase #3 $236.76   13.356%   $268.3817   $268.38   $268.40   $268.40  
  Purchase #4 $244.58   6.702%   $260.9718   $260.97   $260.95   $261.00  
  Purchase #5 $197.88   6.208%   $210.1644   $210.16   $210.15   $210.20  
  Purchase #6 $193.71   9.257%   $211.6417   $211.64   $211.65   $211.60  
  Purchase #7 $24.25   9.232%   $26.4888   $26.49   $26.50   $26.50  
  7 purchase totals = $1,061.14       $1,153.5862   $1,153.58   $1,153.60   $1,153.60