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 $246.59   3.397%   $254.9667   $254.97   $254.95   $255.00  
  Purchase #2 $194.77   8.186%   $210.7139   $210.71   $210.70   $210.70  
  Purchase #3 $182.36   5.442%   $192.284   $192.28   $192.30   $192.30  
  Purchase #4 $114.31   6.175%   $121.3686   $121.37   $121.35   $121.40  
  Purchase #5 $55.61   10.473%   $61.434   $61.43   $61.45   $61.40  
  Purchase #6 $179.88   10.803%   $199.3124   $199.31   $199.30   $199.30  
  Purchase #7 $64.62   5.130%   $67.935   $67.94   $67.95   $67.90  
  7 purchase totals = $1,038.14       $1,108.0146   $1,108.01   $1,108.00   $1,108.00