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 $168.29   10.782%   $186.435   $186.44   $186.45   $186.40  
  Purchase #2 $126.51   4.300%   $131.9499   $131.95   $131.95   $131.90  
  Purchase #3 $104.67   8.707%   $113.7836   $113.78   $113.80   $113.80  
  Purchase #4 $229.46   4.285%   $239.2924   $239.29   $239.30   $239.30  
  Purchase #5 $239.40   4.174%   $249.3926   $249.39   $249.40   $249.40  
  Purchase #6 $91.65   13.648%   $104.1584   $104.16   $104.15   $104.20  
  Purchase #7 $163.60   11.550%   $182.4958   $182.50   $182.50   $182.50  
  7 purchase totals = $1,123.58       $1,207.5077   $1,207.51   $1,207.55   $1,207.50