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 $86.95   6.316%   $92.4418   $92.44   $92.45   $92.40  
  Purchase #2 $235.86   6.533%   $251.2687   $251.27   $251.25   $251.30  
  Purchase #3 $54.95   6.250%   $58.3844   $58.38   $58.40   $58.40  
  Purchase #4 $212.27   12.142%   $238.0438   $238.04   $238.05   $238.00  
  Purchase #5 $215.40   3.575%   $223.1006   $223.10   $223.10   $223.10  
  Purchase #6 $186.76   4.489%   $195.1437   $195.14   $195.15   $195.10  
  Purchase #7 $170.78   7.159%   $183.0061   $183.01   $183.00   $183.00  
  7 purchase totals = $1,162.97       $1,241.3891   $1,241.38   $1,241.40   $1,241.30