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 $195.70   5.759%   $206.9704   $206.97   $206.95   $207.00  
  Purchase #2 $67.63   12.336%   $75.9728   $75.97   $75.95   $76.00  
  Purchase #3 $198.65   5.181%   $208.9421   $208.94   $208.95   $208.90  
  Purchase #4 $191.50   4.566%   $200.2439   $200.24   $200.25   $200.20  
  Purchase #5 $99.41   13.466%   $112.7966   $112.80   $112.80   $112.80  
  Purchase #6 $210.69   9.554%   $230.8193   $230.82   $230.80   $230.80  
  Purchase #7 $120.29   11.531%   $134.1606   $134.16   $134.15   $134.20  
  7 purchase totals = $1,083.87       $1,169.9057   $1,169.90   $1,169.85   $1,169.90