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 $107.87   10.651%   $119.3592   $119.36   $119.35   $119.40  
  Purchase #2 $190.49   11.527%   $212.4478   $212.45   $212.45   $212.40  
  Purchase #3 $201.64   4.645%   $211.0062   $211.01   $211.00   $211.00  
  Purchase #4 $64.32   5.630%   $67.9412   $67.94   $67.95   $67.90  
  Purchase #5 $181.73   13.787%   $206.7851   $206.79   $206.80   $206.80  
  Purchase #6 $208.31   3.829%   $216.2862   $216.29   $216.30   $216.30  
  Purchase #7 $244.70   6.836%   $261.4277   $261.43   $261.45   $261.40  
  7 purchase totals = $1,199.06       $1,295.2534   $1,295.27   $1,295.30   $1,295.20