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 $110.60   11.871%   $123.7293   $123.73   $123.75   $123.70  
  Purchase #2 $183.67   10.792%   $203.4917   $203.49   $203.50   $203.50  
  Purchase #3 $218.99   5.561%   $231.168   $231.17   $231.15   $231.20  
  Purchase #4 $121.29   12.388%   $136.3154   $136.32   $136.30   $136.30  
  Purchase #5 $73.63   7.736%   $79.326   $79.33   $79.35   $79.30  
  Purchase #6 $150.47   4.874%   $157.8039   $157.80   $157.80   $157.80  
  Purchase #7 $150.68   8.465%   $163.4351   $163.44   $163.45   $163.40  
  7 purchase totals = $1,009.33       $1,095.2694   $1,095.28   $1,095.30   $1,095.20