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 $237.28   7.205%   $254.376   $254.38   $254.40   $254.40  
  Purchase #2 $75.33   12.439%   $84.7003   $84.70   $84.70   $84.70  
  Purchase #3 $126.96   4.104%   $132.1704   $132.17   $132.15   $132.20  
  Purchase #4 $40.63   13.564%   $46.1411   $46.14   $46.15   $46.10  
  Purchase #5 $53.37   3.648%   $55.3169   $55.32   $55.30   $55.30  
  Purchase #6 $191.51   7.770%   $206.3903   $206.39   $206.40   $206.40  
  Purchase #7 $207.89   13.123%   $235.1714   $235.17   $235.15   $235.20  
  7 purchase totals = $932.97       $1,014.2664   $1,014.27   $1,014.25   $1,014.30