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 $84.34   13.429%   $95.666   $95.67   $95.65   $95.70  
  Purchase #2 $102.98   8.281%   $111.5078   $111.51   $111.50   $111.50  
  Purchase #3 $99.55   4.759%   $104.2876   $104.29   $104.30   $104.30  
  Purchase #4 $136.29   3.610%   $141.2101   $141.21   $141.20   $141.20  
  Purchase #5 $34.81   12.157%   $39.0419   $39.04   $39.05   $39.00  
  Purchase #6 $80.67   9.154%   $88.0545   $88.05   $88.05   $88.10  
  Purchase #7 $178.89   13.580%   $203.1833   $203.18   $203.20   $203.20  
  7 purchase totals = $717.53       $782.9512   $782.95   $782.95   $783.00