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 $172.75   13.434%   $195.9572   $195.96   $195.95   $196.00  
  Purchase #2 $95.83   9.405%   $104.8428   $104.84   $104.85   $104.80  
  Purchase #3 $153.96   9.813%   $169.0681   $169.07   $169.05   $169.10  
  Purchase #4 $237.80   5.335%   $250.4866   $250.49   $250.50   $250.50  
  Purchase #5 $226.91   12.817%   $255.9931   $255.99   $256.00   $256.00  
  Purchase #6 $110.54   7.275%   $118.5818   $118.58   $118.60   $118.60  
  Purchase #7 $54.40   5.763%   $57.5351   $57.54   $57.55   $57.50  
  7 purchase totals = $1,052.19       $1,152.4647   $1,152.47   $1,152.50   $1,152.50