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 $219.73   7.756%   $236.7723   $236.77   $236.75   $236.80  
  Purchase #2 $94.68   9.145%   $103.3385   $103.34   $103.35   $103.30  
  Purchase #3 $228.82   10.458%   $252.75   $252.75   $252.75   $252.80  
  Purchase #4 $160.26   3.691%   $166.1752   $166.18   $166.20   $166.20  
  Purchase #5 $246.92   6.481%   $262.9229   $262.92   $262.90   $262.90  
  Purchase #6 $196.72   5.345%   $207.2347   $207.23   $207.25   $207.20  
  Purchase #7 $29.89   9.147%   $32.624   $32.62   $32.60   $32.60  
  7 purchase totals = $1,177.02       $1,261.8176   $1,261.81   $1,261.80   $1,261.80