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 $208.57   13.679%   $237.1003   $237.10   $237.10   $237.10  
  Purchase #2 $21.60   10.559%   $23.8807   $23.88   $23.90   $23.90  
  Purchase #3 $97.50   8.219%   $105.5135   $105.51   $105.50   $105.50  
  Purchase #4 $112.47   3.538%   $116.4492   $116.45   $116.45   $116.40  
  Purchase #5 $167.43   3.586%   $173.434   $173.43   $173.45   $173.40  
  Purchase #6 $138.44   12.266%   $155.4211   $155.42   $155.40   $155.40  
  Purchase #7 $208.96   5.626%   $220.7161   $220.72   $220.70   $220.70  
  7 purchase totals = $954.97       $1,032.5149   $1,032.51   $1,032.50   $1,032.40