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 $124.59   6.397%   $132.56   $132.56   $132.55   $132.60  
  Purchase #2 $176.69   4.532%   $184.6976   $184.70   $184.70   $184.70  
  Purchase #3 $5.40   8.479%   $5.8579   $5.86   $5.85   $5.90  
  Purchase #4 $236.43   13.121%   $267.452   $267.45   $267.45   $267.50  
  Purchase #5 $217.71   3.340%   $224.9815   $224.98   $225.00   $225.00  
  Purchase #6 $153.34   3.477%   $158.6716   $158.67   $158.65   $158.70  
  Purchase #7 $219.27   9.602%   $240.3243   $240.32   $240.30   $240.30  
  7 purchase totals = $1,133.43       $1,214.5449   $1,214.54   $1,214.50   $1,214.70