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 $41.82   11.212%   $46.5089   $46.51   $46.50   $46.50  
  Purchase #2 $213.93   12.806%   $241.3259   $241.33   $241.35   $241.30  
  Purchase #3 $163.35   9.532%   $178.9205   $178.92   $178.90   $178.90  
  Purchase #4 $199.51   3.506%   $206.5048   $206.50   $206.50   $206.50  
  Purchase #5 $24.95   12.832%   $28.1516   $28.15   $28.15   $28.20  
  Purchase #6 $22.39   10.345%   $24.7062   $24.71   $24.70   $24.70  
  Purchase #7 $188.88   8.839%   $205.5751   $205.58   $205.60   $205.60  
  7 purchase totals = $854.83       $931.6930   $931.70   $931.70   $931.70