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 $235.30   7.203%   $252.2487   $252.25   $252.25   $252.20  
  Purchase #2 $93.53   13.690%   $106.3343   $106.33   $106.35   $106.30  
  Purchase #3 $182.33   9.290%   $199.2685   $199.27   $199.25   $199.30  
  Purchase #4 $152.57   4.588%   $159.5699   $159.57   $159.55   $159.60  
  Purchase #5 $46.38   11.434%   $51.6831   $51.68   $51.70   $51.70  
  Purchase #6 $170.87   12.602%   $192.403   $192.40   $192.40   $192.40  
  Purchase #7 $215.91   11.701%   $241.1736   $241.17   $241.15   $241.20  
  7 purchase totals = $1,096.89       $1,202.6811   $1,202.67   $1,202.65   $1,202.70