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 $44.59   4.681%   $46.6773   $46.68   $46.70   $46.70  
  Purchase #2 $56.29   13.604%   $63.9477   $63.95   $63.95   $63.90  
  Purchase #3 $216.83   8.837%   $235.9913   $235.99   $236.00   $236.00  
  Purchase #4 $200.86   13.235%   $227.4438   $227.44   $227.45   $227.40  
  Purchase #5 $63.51   6.337%   $67.5346   $67.53   $67.55   $67.50  
  Purchase #6 $35.82   11.361%   $39.8895   $39.89   $39.90   $39.90  
  Purchase #7 $12.62   6.133%   $13.394   $13.39   $13.40   $13.40  
  7 purchase totals = $630.52       $694.8782   $694.87   $694.95   $694.80