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 $84.26   12.742%   $94.9964   $95.00   $95.00   $95.00  
  Purchase #2 $157.71   3.356%   $163.0027   $163.00   $163.00   $163.00  
  Purchase #3 $85.54   4.363%   $89.2721   $89.27   $89.25   $89.30  
  Purchase #4 $47.55   3.458%   $49.1943   $49.19   $49.20   $49.20  
  Purchase #5 $62.74   11.331%   $69.8491   $69.85   $69.85   $69.80  
  Purchase #6 $161.79   4.314%   $168.7696   $168.77   $168.75   $168.80  
  Purchase #7 $140.88   3.836%   $146.2842   $146.28   $146.30   $146.30  
  7 purchase totals = $740.47       $781.3684   $781.36   $781.35   $781.40