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 $87.34   9.510%   $95.646   $95.65   $95.65   $95.60  
  Purchase #2 $132.39   5.614%   $139.8224   $139.82   $139.80   $139.80  
  Purchase #3 $70.37   7.546%   $75.6801   $75.68   $75.70   $75.70  
  Purchase #4 $29.48   13.382%   $33.425   $33.43   $33.45   $33.40  
  Purchase #5 $244.93   8.736%   $266.3271   $266.33   $266.35   $266.30  
  Purchase #6 $194.76   12.636%   $219.3699   $219.37   $219.35   $219.40  
  Purchase #7 $165.30   10.348%   $182.4052   $182.41   $182.40   $182.40  
  7 purchase totals = $924.57       $1,012.6757   $1,012.69   $1,012.70   $1,012.60