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 $46.70   5.416%   $49.2293   $49.23   $49.25   $49.20  
  Purchase #2 $92.49   9.780%   $101.5355   $101.54   $101.55   $101.50  
  Purchase #3 $200.29   9.198%   $218.7127   $218.71   $218.70   $218.70  
  Purchase #4 $79.45   9.686%   $87.1455   $87.15   $87.15   $87.10  
  Purchase #5 $9.47   11.341%   $10.544   $10.54   $10.55   $10.50  
  Purchase #6 $210.92   4.551%   $220.519   $220.52   $220.50   $220.50  
  Purchase #7 $75.61   5.137%   $79.4941   $79.49   $79.50   $79.50  
  7 purchase totals = $714.93       $767.1801   $767.18   $767.20   $767.00