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 $62.85   10.276%   $69.3085   $69.31   $69.30   $69.30  
  Purchase #2 $218.96   6.292%   $232.737   $232.74   $232.75   $232.70  
  Purchase #3 $93.71   12.410%   $105.3394   $105.34   $105.35   $105.30  
  Purchase #4 $153.38   13.272%   $173.7366   $173.74   $173.75   $173.70  
  Purchase #5 $75.98   7.262%   $81.4977   $81.50   $81.50   $81.50  
  Purchase #6 $154.66   5.171%   $162.6575   $162.66   $162.65   $162.70  
  Purchase #7 $110.48   5.535%   $116.5951   $116.60   $116.60   $116.60  
  7 purchase totals = $870.02       $941.8718   $941.89   $941.90   $941.80