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 $67.81   10.588%   $74.9897   $74.99   $75.00   $75.00  
  Purchase #2 $94.27   11.375%   $104.9932   $104.99   $105.00   $105.00  
  Purchase #3 $246.55   11.651%   $275.2755   $275.28   $275.30   $275.30  
  Purchase #4 $162.49   3.245%   $167.7628   $167.76   $167.75   $167.80  
  Purchase #5 $167.97   11.329%   $186.9993   $187.00   $187.00   $187.00  
  Purchase #6 $101.59   8.800%   $110.5299   $110.53   $110.55   $110.50  
  Purchase #7 $96.26   5.407%   $101.4648   $101.46   $101.45   $101.50  
  7 purchase totals = $936.94       $1,022.0152   $1,022.01   $1,022.05   $1,022.10