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 $68.51   13.185%   $77.543   $77.54   $77.55   $77.50  
  Purchase #2 $118.82   5.435%   $125.2779   $125.28   $125.30   $125.30  
  Purchase #3 $49.63   3.472%   $51.3532   $51.35   $51.35   $51.40  
  Purchase #4 $182.65   5.772%   $193.1926   $193.19   $193.20   $193.20  
  Purchase #5 $207.64   10.315%   $229.0581   $229.06   $229.05   $229.10  
  Purchase #6 $34.68   7.595%   $37.3139   $37.31   $37.30   $37.30  
  Purchase #7 $37.44   11.763%   $41.8441   $41.84   $41.85   $41.80  
  7 purchase totals = $699.37       $755.5828   $755.57   $755.60   $755.60