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 $181.33   6.815%   $193.6876   $193.69   $193.70   $193.70  
  Purchase #2 $71.89   6.696%   $76.7038   $76.70   $76.70   $76.70  
  Purchase #3 $39.71   10.302%   $43.8009   $43.80   $43.80   $43.80  
  Purchase #4 $94.69   7.339%   $101.6393   $101.64   $101.65   $101.60  
  Purchase #5 $48.48   9.597%   $53.1326   $53.13   $53.15   $53.10  
  Purchase #6 $85.91   7.853%   $92.6565   $92.66   $92.65   $92.70  
  Purchase #7 $184.42   11.277%   $205.217   $205.22   $205.20   $205.20  
  7 purchase totals = $706.43       $766.8377   $766.84   $766.85   $766.80