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 $116.81   7.824%   $125.9492   $125.95   $125.95   $125.90  
  Purchase #2 $178.45   4.407%   $186.3143   $186.31   $186.30   $186.30  
  Purchase #3 $248.92   5.344%   $262.2223   $262.22   $262.20   $262.20  
  Purchase #4 $34.43   13.475%   $39.0694   $39.07   $39.05   $39.10  
  Purchase #5 $67.69   13.357%   $76.7314   $76.73   $76.75   $76.70  
  Purchase #6 $108.73   9.385%   $118.9343   $118.93   $118.95   $118.90  
  Purchase #7 $196.47   3.232%   $202.8199   $202.82   $202.80   $202.80  
  7 purchase totals = $951.50       $1,012.0408   $1,012.03   $1,012.00   $1,011.90