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 $107.46   11.612%   $119.9383   $119.94   $119.95   $119.90  
  Purchase #2 $194.94   8.746%   $211.9895   $211.99   $212.00   $212.00  
  Purchase #3 $114.38   8.383%   $123.9685   $123.97   $123.95   $124.00  
  Purchase #4 $208.65   13.460%   $236.7343   $236.73   $236.75   $236.70  
  Purchase #5 $51.85   6.486%   $55.213   $55.21   $55.20   $55.20  
  Purchase #6 $23.46   12.750%   $26.4512   $26.45   $26.45   $26.50  
  Purchase #7 $229.88   9.146%   $250.9048   $250.90   $250.90   $250.90  
  7 purchase totals = $930.62       $1,025.1996   $1,025.19   $1,025.20   $1,025.20