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	$51.27	3.863%	$53.2506	$53.25	$53.25	$53.30
Purchase #2	$60.34	8.606%	$65.5329	$65.53	$65.55	$65.50
Purchase #3	$124.53	11.863%	$139.303	$139.30	$139.30	$139.30
Purchase #4	$197.53	11.281%	$219.8134	$219.81	$219.80	$219.80
Purchase #5	$30.75	3.358%	$31.7826	$31.78	$31.80	$31.80
Purchase #6	$143.78	10.451%	$158.8064	$158.81	$158.80	$158.80
Purchase #7	$55.30	13.587%	$62.8136	$62.81	$62.80	$62.80
7 purchase totals =	$663.50		$731.3025	$731.29	$731.30	$731.30