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 $83.74   12.661%   $94.3423   $94.34   $94.35   $94.30  
  Purchase #2 $225.45   4.184%   $234.8828   $234.88   $234.90   $234.90  
  Purchase #3 $147.73   3.859%   $153.4309   $153.43   $153.45   $153.40  
  Purchase #4 $120.54   5.574%   $127.2589   $127.26   $127.25   $127.30  
  Purchase #5 $45.69   11.194%   $50.8045   $50.80   $50.80   $50.80  
  Purchase #6 $182.88   6.220%   $194.2551   $194.26   $194.25   $194.30  
  Purchase #7 $247.49   5.844%   $261.9533   $261.95   $261.95   $262.00  
  7 purchase totals = $1,053.52       $1,116.9278   $1,116.92   $1,116.95   $1,117.00