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 $91.46   4.578%   $95.647   $95.65   $95.65   $95.60  
  Purchase #2 $221.99   7.240%   $238.0621   $238.06   $238.05   $238.10  
  Purchase #3 $71.72   4.636%   $75.0449   $75.04   $75.05   $75.00  
  Purchase #4 $122.51   4.403%   $127.9041   $127.90   $127.90   $127.90  
  Purchase #5 $111.95   8.216%   $121.1478   $121.15   $121.15   $121.10  
  Purchase #6 $114.36   8.306%   $123.8587   $123.86   $123.85   $123.90  
  Purchase #7 $97.54   13.412%   $110.6221   $110.62   $110.60   $110.60  
  7 purchase totals = $831.53       $892.2867   $892.28   $892.25   $892.20