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 $62.87   6.705%   $67.0854   $67.09   $67.10   $67.10  
  Purchase #2 $238.99   6.578%   $254.7108   $254.71   $254.70   $254.70  
  Purchase #3 $188.54   3.302%   $194.7656   $194.77   $194.75   $194.80  
  Purchase #4 $188.33   13.272%   $213.3252   $213.33   $213.35   $213.30  
  Purchase #5 $42.31   12.783%   $47.7185   $47.72   $47.70   $47.70  
  Purchase #6 $15.77   13.549%   $17.9067   $17.91   $17.90   $17.90  
  Purchase #7 $151.68   5.160%   $159.5067   $159.51   $159.50   $159.50  
  7 purchase totals = $888.49       $955.0189   $955.04   $955.00   $955.00