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 $193.41   4.793%   $202.6801   $202.68   $202.70   $202.70  
  Purchase #2 $43.85   13.190%   $49.6338   $49.63   $49.65   $49.60  
  Purchase #3 $126.75   11.241%   $140.998   $141.00   $141.00   $141.00  
  Purchase #4 $199.41   13.130%   $225.5925   $225.59   $225.60   $225.60  
  Purchase #5 $214.34   3.702%   $222.2749   $222.27   $222.25   $222.30  
  Purchase #6 $224.91   8.593%   $244.2365   $244.24   $244.25   $244.20  
  Purchase #7 $53.33   9.143%   $58.206   $58.21   $58.20   $58.20  
  7 purchase totals = $1,056.00       $1,143.6218   $1,143.62   $1,143.65   $1,143.60