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 $60.58   7.403%   $65.0647   $65.06   $65.05   $65.10  
  Purchase #2 $194.77   7.547%   $209.4693   $209.47   $209.45   $209.50  
  Purchase #3 $212.85   3.873%   $221.0937   $221.09   $221.10   $221.10  
  Purchase #4 $215.48   4.319%   $224.7866   $224.79   $224.80   $224.80  
  Purchase #5 $84.81   3.646%   $87.9022   $87.90   $87.90   $87.90  
  Purchase #6 $95.60   5.682%   $101.032   $101.03   $101.05   $101.00  
  Purchase #7 $53.89   5.518%   $56.8637   $56.86   $56.85   $56.90  
  7 purchase totals = $917.98       $966.2122   $966.20   $966.20   $966.30