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 $157.98   10.525%   $174.6074   $174.61   $174.60   $174.60  
  Purchase #2 $91.67   12.124%   $102.7841   $102.78   $102.80   $102.80  
  Purchase #3 $67.86   8.407%   $73.565   $73.57   $73.55   $73.60  
  Purchase #4 $29.91   13.237%   $33.8692   $33.87   $33.85   $33.90  
  Purchase #5 $215.38   5.530%   $227.2905   $227.29   $227.30   $227.30  
  Purchase #6 $107.73   7.763%   $116.0931   $116.09   $116.10   $116.10  
  Purchase #7 $26.49   12.219%   $29.7268   $29.73   $29.75   $29.70  
  7 purchase totals = $697.02       $757.9361   $757.94   $757.95   $758.00