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 $44.43   9.281%   $48.5535   $48.55   $48.55   $48.60  
  Purchase #2 $225.41   9.694%   $247.2612   $247.26   $247.25   $247.30  
  Purchase #3 $215.55   9.251%   $235.4905   $235.49   $235.50   $235.50  
  Purchase #4 $199.92   5.489%   $210.8936   $210.89   $210.90   $210.90  
  Purchase #5 $224.91   12.685%   $253.4398   $253.44   $253.45   $253.40  
  Purchase #6 $124.26   6.617%   $132.4823   $132.48   $132.50   $132.50  
  Purchase #7 $7.65   6.427%   $8.1417   $8.14   $8.15   $8.10  
  7 purchase totals = $1,042.13       $1,136.2626   $1,136.25   $1,136.30   $1,136.30