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 $86.25   11.226%   $95.9324   $95.93   $95.95   $95.90  
  Purchase #2 $206.59   4.299%   $215.4713   $215.47   $215.45   $215.50  
  Purchase #3 $73.26   3.751%   $76.008   $76.01   $76.00   $76.00  
  Purchase #4 $221.78   3.557%   $229.6687   $229.67   $229.65   $229.70  
  Purchase #5 $78.42   13.640%   $89.1165   $89.12   $89.10   $89.10  
  Purchase #6 $152.59   7.306%   $163.7382   $163.74   $163.75   $163.70  
  Purchase #7 $214.62   9.372%   $234.7342   $234.73   $234.75   $234.70  
  7 purchase totals = $1,033.51       $1,104.6693   $1,104.67   $1,104.65   $1,104.60