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 $214.87   7.478%   $230.938   $230.94   $230.95   $230.90  
  Purchase #2 $236.64   8.505%   $256.7662   $256.77   $256.75   $256.80  
  Purchase #3 $234.59   9.209%   $256.1934   $256.19   $256.20   $256.20  
  Purchase #4 $205.40   10.206%   $226.3631   $226.36   $226.35   $226.40  
  Purchase #5 $228.25   10.552%   $252.3349   $252.33   $252.35   $252.30  
  Purchase #6 $228.85   8.792%   $248.9705   $248.97   $248.95   $249.00  
  Purchase #7 $225.65   6.833%   $241.0687   $241.07   $241.05   $241.10  
  7 purchase totals = $1,574.25       $1,712.6348   $1,712.63   $1,712.60   $1,712.70