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 $188.50   3.845%   $195.7478   $195.75   $195.75   $195.70  
  Purchase #2 $72.82   4.870%   $76.3663   $76.37   $76.35   $76.40  
  Purchase #3 $239.86   12.634%   $270.1639   $270.16   $270.15   $270.20  
  Purchase #4 $68.42   6.631%   $72.9569   $72.96   $72.95   $73.00  
  Purchase #5 $87.32   11.761%   $97.5897   $97.59   $97.60   $97.60  
  Purchase #6 $95.27   12.123%   $106.8196   $106.82   $106.80   $106.80  
  Purchase #7 $241.60   8.533%   $262.2157   $262.22   $262.20   $262.20  
  7 purchase totals = $993.79       $1,081.8599   $1,081.87   $1,081.80   $1,081.90