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 $102.55   11.278%   $114.1156   $114.12   $114.10   $114.10  
  Purchase #2 $247.74   12.759%   $279.3491   $279.35   $279.35   $279.30  
  Purchase #3 $244.73   4.738%   $256.3253   $256.33   $256.35   $256.30  
  Purchase #4 $76.97   8.522%   $83.5294   $83.53   $83.55   $83.50  
  Purchase #5 $115.39   4.594%   $120.691   $120.69   $120.70   $120.70  
  Purchase #6 $159.39   8.846%   $173.4896   $173.49   $173.50   $173.50  
  Purchase #7 $119.43   5.796%   $126.3522   $126.35   $126.35   $126.40  
  7 purchase totals = $1,066.20       $1,153.8522   $1,153.86   $1,153.90   $1,153.80