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 $181.66   7.675%   $195.6024   $195.60   $195.60   $195.60  
  Purchase #2 $210.82   3.792%   $218.8143   $218.81   $218.80   $218.80  
  Purchase #3 $139.92   4.847%   $146.7019   $146.70   $146.70   $146.70  
  Purchase #4 $5.77   12.265%   $6.4777   $6.48   $6.50   $6.50  
  Purchase #5 $85.87   7.490%   $92.3017   $92.30   $92.30   $92.30  
  Purchase #6 $171.71   3.448%   $177.6306   $177.63   $177.65   $177.60  
  Purchase #7 $155.89   11.502%   $173.8205   $173.82   $173.80   $173.80  
  7 purchase totals = $951.64       $1,011.3491   $1,011.34   $1,011.35   $1,011.30