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 $46.47   5.290%   $48.9283   $48.93   $48.95   $48.90  
  Purchase #2 $221.98   4.668%   $232.342   $232.34   $232.35   $232.30  
  Purchase #3 $241.61   10.179%   $266.2035   $266.20   $266.20   $266.20  
  Purchase #4 $67.48   10.566%   $74.6099   $74.61   $74.60   $74.60  
  Purchase #5 $140.84   5.776%   $148.9749   $148.97   $148.95   $149.00  
  Purchase #6 $183.56   4.246%   $191.354   $191.35   $191.35   $191.40  
  Purchase #7 $95.29   10.706%   $105.4917   $105.49   $105.50   $105.50  
  7 purchase totals = $997.23       $1,067.9043   $1,067.89   $1,067.90   $1,067.90