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	$127.40	9.660%	$139.7068	$139.71	$139.70	$139.70
Purchase #2	$84.52	9.574%	$92.6119	$92.61	$92.60	$92.60
Purchase #3	$73.53	11.389%	$81.9043	$81.90	$81.90	$81.90
Purchase #4	$93.78	11.647%	$104.7026	$104.70	$104.70	$104.70
Purchase #5	$136.25	4.800%	$142.79	$142.79	$142.80	$142.80
Purchase #6	$209.39	7.265%	$224.6022	$224.60	$224.60	$224.60
Purchase #7	$238.59	4.597%	$249.558	$249.56	$249.55	$249.60
7 purchase totals =	$963.46		$1,035.8758	$1,035.87	$1,035.85	$1,035.90