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	$162.77	10.125%	$179.2505	$179.25	$179.25	$179.30
Purchase #2	$63.91	6.717%	$68.2028	$68.20	$68.20	$68.20
Purchase #3	$137.79	10.828%	$152.7099	$152.71	$152.70	$152.70
Purchase #4	$42.31	9.783%	$46.4492	$46.45	$46.45	$46.40
Purchase #5	$102.88	8.758%	$111.8902	$111.89	$111.90	$111.90
Purchase #6	$243.93	5.422%	$257.1559	$257.16	$257.15	$257.20
Purchase #7	$228.26	11.533%	$254.5852	$254.59	$254.60	$254.60
7 purchase totals =	$981.85		$1,070.2437	$1,070.25	$1,070.25	$1,070.30