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 $152.66   10.863%   $169.2435   $169.24   $169.25   $169.20  
  Purchase #2 $228.74   10.149%   $251.9548   $251.95   $251.95   $252.00  
  Purchase #3 $119.53   10.554%   $132.1452   $132.15   $132.15   $132.10  
  Purchase #4 $112.96   6.775%   $120.613   $120.61   $120.60   $120.60  
  Purchase #5 $147.85   8.296%   $160.1156   $160.12   $160.10   $160.10  
  Purchase #6 $104.90   5.792%   $110.9758   $110.98   $111.00   $111.00  
  Purchase #7 $206.56   7.474%   $221.9983   $222.00   $222.00   $222.00  
  7 purchase totals = $1,073.20       $1,167.0462   $1,167.05   $1,167.05   $1,167.00