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 $197.62   6.586%   $210.6353   $210.64   $210.65   $210.60  
  Purchase #2 $230.74   5.279%   $242.9208   $242.92   $242.90   $242.90  
  Purchase #3 $50.43   4.865%   $52.8834   $52.88   $52.90   $52.90  
  Purchase #4 $105.38   6.621%   $112.3572   $112.36   $112.35   $112.40  
  Purchase #5 $73.40   4.796%   $76.9203   $76.92   $76.90   $76.90  
  Purchase #6 $116.50   7.829%   $125.6208   $125.62   $125.60   $125.60  
  Purchase #7 $224.41   6.498%   $238.9922   $238.99   $239.00   $239.00  
  7 purchase totals = $998.48       $1,060.3300   $1,060.33   $1,060.30   $1,060.30