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 $56.26   10.460%   $62.1448   $62.14   $62.15   $62.10  
  Purchase #2 $125.61   5.859%   $132.9695   $132.97   $132.95   $133.00  
  Purchase #3 $50.30   8.358%   $54.5041   $54.50   $54.50   $54.50  
  Purchase #4 $200.78   7.514%   $215.8666   $215.87   $215.85   $215.90  
  Purchase #5 $33.80   12.219%   $37.93   $37.93   $37.95   $37.90  
  Purchase #6 $64.85   4.114%   $67.5179   $67.52   $67.50   $67.50  
  Purchase #7 $192.40   9.721%   $211.1032   $211.10   $211.10   $211.10  
  7 purchase totals = $724.00       $782.0361   $782.03   $782.00   $782.00