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 $167.44   10.463%   $184.9592   $184.96   $184.95   $185.00  
  Purchase #2 $107.45   11.390%   $119.6886   $119.69   $119.70   $119.70  
  Purchase #3 $113.73   5.448%   $119.926   $119.93   $119.95   $119.90  
  Purchase #4 $126.60   3.371%   $130.8677   $130.87   $130.85   $130.90  
  Purchase #5 $131.87   7.352%   $141.5651   $141.57   $141.55   $141.60  
  Purchase #6 $191.29   4.360%   $199.6302   $199.63   $199.65   $199.60  
  Purchase #7 $247.92   7.317%   $266.0603   $266.06   $266.05   $266.10  
  7 purchase totals = $1,086.30       $1,162.6971   $1,162.71   $1,162.70   $1,162.80