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 $62.48   7.486%   $67.1573   $67.16   $67.15   $67.20  
  Purchase #2 $115.31   3.459%   $119.2986   $119.30   $119.30   $119.30  
  Purchase #3 $230.47   11.820%   $257.7116   $257.71   $257.70   $257.70  
  Purchase #4 $92.80   5.591%   $97.9884   $97.99   $98.00   $98.00  
  Purchase #5 $163.54   5.592%   $172.6852   $172.69   $172.70   $172.70  
  Purchase #6 $13.93   6.783%   $14.8749   $14.87   $14.85   $14.90  
  Purchase #7 $196.88   3.556%   $203.8811   $203.88   $203.90   $203.90  
  7 purchase totals = $875.41       $933.5971   $933.60   $933.60   $933.70