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 $44.53   9.312%   $48.6766   $48.68   $48.70   $48.70  
  Purchase #2 $115.91   8.210%   $125.4262   $125.43   $125.45   $125.40  
  Purchase #3 $24.32   3.602%   $25.196   $25.20   $25.20   $25.20  
  Purchase #4 $225.25   9.715%   $247.133   $247.13   $247.15   $247.10  
  Purchase #5 $244.78   7.722%   $263.6819   $263.68   $263.70   $263.70  
  Purchase #6 $222.65   10.349%   $245.692   $245.69   $245.70   $245.70  
  Purchase #7 $108.59   5.162%   $114.1954   $114.20   $114.20   $114.20  
  7 purchase totals = $986.03       $1,070.0011   $1,070.01   $1,070.10   $1,070.00