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	$124.78	8.281%	$135.113	$135.11	$135.10	$135.10
Purchase #2	$131.87	12.573%	$148.45	$148.45	$148.45	$148.50
Purchase #3	$70.51	6.684%	$75.2229	$75.22	$75.20	$75.20
Purchase #4	$170.95	9.388%	$186.9988	$187.00	$187.00	$187.00
Purchase #5	$101.35	10.327%	$111.8164	$111.82	$111.80	$111.80
Purchase #6	$99.32	9.515%	$108.7703	$108.77	$108.75	$108.80
Purchase #7	$227.65	9.844%	$250.0599	$250.06	$250.05	$250.10
7 purchase totals =	$926.43		$1,016.4313	$1,016.43	$1,016.35	$1,016.50