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 $212.47   5.679%   $224.5362   $224.54   $224.55   $224.50  
  Purchase #2 $6.75   7.643%   $7.2659   $7.27   $7.25   $7.30  
  Purchase #3 $153.86   13.180%   $174.1387   $174.14   $174.15   $174.10  
  Purchase #4 $114.80   5.246%   $120.8224   $120.82   $120.80   $120.80  
  Purchase #5 $189.60   13.481%   $215.16   $215.16   $215.15   $215.20  
  Purchase #6 $161.66   5.274%   $170.1859   $170.19   $170.20   $170.20  
  Purchase #7 $182.43   9.192%   $199.199   $199.20   $199.20   $199.20  
  7 purchase totals = $1,021.57       $1,111.3081   $1,111.32   $1,111.30   $1,111.30