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 $84.99   11.771%   $94.9942   $94.99   $95.00   $95.00  
  Purchase #2 $230.72   8.256%   $249.7682   $249.77   $249.75   $249.80  
  Purchase #3 $143.27   4.609%   $149.8733   $149.87   $149.85   $149.90  
  Purchase #4 $36.32   3.618%   $37.6341   $37.63   $37.65   $37.60  
  Purchase #5 $187.81   11.523%   $209.4513   $209.45   $209.45   $209.50  
  Purchase #6 $6.87   8.575%   $7.4591   $7.46   $7.45   $7.50  
  Purchase #7 $172.80   6.487%   $184.0095   $184.01   $184.00   $184.00  
  7 purchase totals = $862.78       $933.1897   $933.18   $933.15   $933.30