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 $125.66   5.307%   $132.3288   $132.33   $132.35   $132.30  
  Purchase #2 $111.85   11.196%   $124.3727   $124.37   $124.35   $124.40  
  Purchase #3 $60.77   11.135%   $67.5367   $67.54   $67.55   $67.50  
  Purchase #4 $200.63   11.714%   $224.1318   $224.13   $224.15   $224.10  
  Purchase #5 $245.70   7.172%   $263.3216   $263.32   $263.30   $263.30  
  Purchase #6 $71.92   13.749%   $81.8083   $81.81   $81.80   $81.80  
  Purchase #7 $219.77   10.197%   $242.1799   $242.18   $242.20   $242.20  
  7 purchase totals = $1,036.30       $1,135.6798   $1,135.68   $1,135.70   $1,135.60