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 $188.38   6.153%   $199.971   $199.97   $199.95   $200.00  
  Purchase #2 $239.74   6.228%   $254.671   $254.67   $254.65   $254.70  
  Purchase #3 $116.29   13.616%   $132.124   $132.12   $132.10   $132.10  
  Purchase #4 $146.66   8.550%   $159.1994   $159.20   $159.20   $159.20  
  Purchase #5 $170.76   8.126%   $184.636   $184.64   $184.65   $184.60  
  Purchase #6 $11.51   5.615%   $12.1563   $12.16   $12.15   $12.20  
  Purchase #7 $198.37   4.743%   $207.7787   $207.78   $207.80   $207.80  
  7 purchase totals = $1,071.71       $1,150.5364   $1,150.54   $1,150.50   $1,150.60