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	$131.68	7.492%	$141.5455	$141.55	$141.55	$141.50
Purchase #2	$66.90	3.740%	$69.4021	$69.40	$69.40	$69.40
Purchase #3	$85.84	4.159%	$89.4101	$89.41	$89.40	$89.40
Purchase #4	$56.29	6.211%	$59.7862	$59.79	$59.80	$59.80
Purchase #5	$94.66	5.774%	$100.1257	$100.13	$100.15	$100.10
Purchase #6	$226.68	9.246%	$247.6388	$247.64	$247.65	$247.60
Purchase #7	$138.49	13.449%	$157.1155	$157.12	$157.10	$157.10
7 purchase totals =	$800.54		$865.0239	$865.04	$865.05	$864.90