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	$151.69	9.529%	$166.1445	$166.14	$166.15	$166.10
Purchase #2	$175.77	8.557%	$190.8106	$190.81	$190.80	$190.80
Purchase #3	$74.64	5.604%	$78.8228	$78.82	$78.80	$78.80
Purchase #4	$122.65	12.445%	$137.9138	$137.91	$137.90	$137.90
Purchase #5	$93.93	12.845%	$105.9953	$106.00	$106.00	$106.00
Purchase #6	$162.56	4.731%	$170.2507	$170.25	$170.25	$170.30
Purchase #7	$159.72	4.212%	$166.4474	$166.45	$166.45	$166.40
7 purchase totals =	$940.96		$1,016.3851	$1,016.38	$1,016.35	$1,016.30