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 $117.86   6.179%   $125.1426   $125.14   $125.15   $125.10  
  Purchase #2 $169.34   8.561%   $183.8372   $183.84   $183.85   $183.80  
  Purchase #3 $203.77   4.345%   $212.6238   $212.62   $212.60   $212.60  
  Purchase #4 $248.60   7.402%   $267.0014   $267.00   $267.00   $267.00  
  Purchase #5 $67.34   4.777%   $70.5568   $70.56   $70.55   $70.60  
  Purchase #6 $178.32   9.232%   $194.7825   $194.78   $194.80   $194.80  
  Purchase #7 $203.68   5.780%   $215.4527   $215.45   $215.45   $215.50  
  7 purchase totals = $1,188.91       $1,269.3970   $1,269.39   $1,269.40   $1,269.40