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 $63.79   7.541%   $68.6004   $68.60   $68.60   $68.60  
  Purchase #2 $164.79   6.352%   $175.2575   $175.26   $175.25   $175.30  
  Purchase #3 $102.44   9.758%   $112.4361   $112.44   $112.45   $112.40  
  Purchase #4 $162.63   6.442%   $173.1066   $173.11   $173.10   $173.10  
  Purchase #5 $155.80   12.865%   $175.8437   $175.84   $175.85   $175.80  
  Purchase #6 $130.36   13.684%   $148.1985   $148.20   $148.20   $148.20  
  Purchase #7 $93.96   7.731%   $101.224   $101.22   $101.20   $101.20  
  7 purchase totals = $873.77       $954.6668   $954.67   $954.65   $954.60