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 $94.46   8.257%   $102.2596   $102.26   $102.25   $102.30  
  Purchase #2 $244.40   4.706%   $255.9015   $255.90   $255.90   $255.90  
  Purchase #3 $246.75   12.584%   $277.801   $277.80   $277.80   $277.80  
  Purchase #4 $195.31   11.278%   $217.3371   $217.34   $217.35   $217.30  
  Purchase #5 $213.48   4.359%   $222.7856   $222.79   $222.80   $222.80  
  Purchase #6 $151.60   11.500%   $169.034   $169.03   $169.05   $169.00  
  Purchase #7 $195.72   7.735%   $210.8589   $210.86   $210.85   $210.90  
  7 purchase totals = $1,341.72       $1,455.9777   $1,455.98   $1,456.00   $1,456.00