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 $58.88   4.832%   $61.7251   $61.73   $61.75   $61.70  
  Purchase #2 $151.94   4.534%   $158.829   $158.83   $158.85   $158.80  
  Purchase #3 $94.37   7.331%   $101.2883   $101.29   $101.30   $101.30  
  Purchase #4 $227.62   6.164%   $241.6505   $241.65   $241.65   $241.70  
  Purchase #5 $101.96   13.425%   $115.6481   $115.65   $115.65   $115.60  
  Purchase #6 $37.94   11.133%   $42.1639   $42.16   $42.15   $42.20  
  Purchase #7 $185.74   13.690%   $211.1678   $211.17   $211.15   $211.20  
  7 purchase totals = $858.45       $932.4727   $932.48   $932.50   $932.50