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 $88.61   7.166%   $94.9598   $94.96   $94.95   $95.00  
  Purchase #2 $95.34   3.827%   $98.9887   $98.99   $99.00   $99.00  
  Purchase #3 $189.58   11.730%   $211.8177   $211.82   $211.80   $211.80  
  Purchase #4 $157.77   9.709%   $173.0879   $173.09   $173.10   $173.10  
  Purchase #5 $112.39   3.747%   $116.6013   $116.60   $116.60   $116.60  
  Purchase #6 $62.71   4.573%   $65.5777   $65.58   $65.60   $65.60  
  Purchase #7 $157.47   4.846%   $165.101   $165.10   $165.10   $165.10  
  7 purchase totals = $863.87       $926.1341   $926.14   $926.15   $926.20