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   7.434%   $126.6217   $126.62   $126.60   $126.60  
  Purchase #2 $158.35   6.758%   $169.0513   $169.05   $169.05   $169.10  
  Purchase #3 $73.77   12.104%   $82.6991   $82.70   $82.70   $82.70  
  Purchase #4 $195.85   6.698%   $208.968   $208.97   $208.95   $209.00  
  Purchase #5 $238.41   3.340%   $246.3729   $246.37   $246.35   $246.40  
  Purchase #6 $134.38   4.192%   $140.0132   $140.01   $140.00   $140.00  
  Purchase #7 $56.46   10.774%   $62.543   $62.54   $62.55   $62.50  
  7 purchase totals = $975.08       $1,036.2692   $1,036.26   $1,036.20   $1,036.30