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 $60.73   5.261%   $63.925   $63.93   $63.95   $63.90  
  Purchase #2 $222.82   7.132%   $238.7115   $238.71   $238.70   $238.70  
  Purchase #3 $125.97   6.558%   $134.2311   $134.23   $134.25   $134.20  
  Purchase #4 $116.67   11.678%   $130.2947   $130.29   $130.30   $130.30  
  Purchase #5 $121.93   3.109%   $125.7208   $125.72   $125.70   $125.70  
  Purchase #6 $249.49   10.237%   $275.0303   $275.03   $275.05   $275.00  
  Purchase #7 $83.48   10.348%   $92.1185   $92.12   $92.10   $92.10  
  7 purchase totals = $981.09       $1,060.0319   $1,060.03   $1,060.05   $1,059.90