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 $244.83   9.163%   $267.2638   $267.26   $267.25   $267.30  
  Purchase #2 $234.76   5.278%   $247.1506   $247.15   $247.15   $247.20  
  Purchase #3 $213.51   13.369%   $242.0542   $242.05   $242.05   $242.10  
  Purchase #4 $115.30   7.137%   $123.529   $123.53   $123.55   $123.50  
  Purchase #5 $44.53   4.231%   $46.4141   $46.41   $46.40   $46.40  
  Purchase #6 $194.65   8.169%   $210.551   $210.55   $210.55   $210.60  
  Purchase #7 $54.28   11.466%   $60.5037   $60.50   $60.50   $60.50  
  7 purchase totals = $1,101.86       $1,197.4664   $1,197.45   $1,197.45   $1,197.60