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	$53.95	13.874%	$61.435	$61.44	$61.45	$61.40
Purchase #2	$153.59	12.183%	$172.3019	$172.30	$172.30	$172.30
Purchase #3	$19.83	9.427%	$21.6994	$21.70	$21.70	$21.70
Purchase #4	$235.92	11.763%	$263.6713	$263.67	$263.65	$263.70
Purchase #5	$42.31	5.129%	$44.4801	$44.48	$44.50	$44.50
Purchase #6	$55.70	11.532%	$62.1233	$62.12	$62.10	$62.10
Purchase #7	$20.33	7.411%	$21.8367	$21.84	$21.85	$21.80
7 purchase totals =	$581.63		$647.5477	$647.55	$647.55	$647.50