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 $174.73   11.613%   $195.0214   $195.02   $195.00   $195.00  
  Purchase #2 $175.44   4.246%   $182.8892   $182.89   $182.90   $182.90  
  Purchase #3 $200.73   10.271%   $221.347   $221.35   $221.35   $221.30  
  Purchase #4 $64.98   7.111%   $69.6007   $69.60   $69.60   $69.60  
  Purchase #5 $237.56   8.144%   $256.9069   $256.91   $256.90   $256.90  
  Purchase #6 $243.88   8.412%   $264.3952   $264.40   $264.40   $264.40  
  Purchase #7 $196.52   8.863%   $213.9376   $213.94   $213.95   $213.90  
  7 purchase totals = $1,293.84       $1,404.0980   $1,404.11   $1,404.10   $1,404.00