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 $22.38   13.327%   $25.3626   $25.36   $25.35   $25.40  
  Purchase #2 $54.70   10.327%   $60.3489   $60.35   $60.35   $60.30  
  Purchase #3 $156.28   7.747%   $168.387   $168.39   $168.40   $168.40  
  Purchase #4 $110.84   7.371%   $119.01   $119.01   $119.00   $119.00  
  Purchase #5 $155.92   5.504%   $164.5018   $164.50   $164.50   $164.50  
  Purchase #6 $158.93   12.404%   $178.6437   $178.64   $178.65   $178.60  
  Purchase #7 $152.62   10.573%   $168.7565   $168.76   $168.75   $168.80  
  7 purchase totals = $811.67       $885.0105   $885.01   $885.00   $885.00