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	$234.50	9.352%	$256.4304	$256.43	$256.45	$256.40
Purchase #2	$69.96	6.603%	$74.5795	$74.58	$74.60	$74.60
Purchase #3	$143.60	11.222%	$159.7148	$159.71	$159.70	$159.70
Purchase #4	$247.72	7.636%	$266.6359	$266.64	$266.65	$266.60
Purchase #5	$157.54	10.861%	$174.6504	$174.65	$174.65	$174.70
Purchase #6	$105.61	3.674%	$109.4901	$109.49	$109.50	$109.50
Purchase #7	$48.40	9.472%	$52.9844	$52.98	$53.00	$53.00
7 purchase totals =	$1,007.33		$1,094.4855	$1,094.48	$1,094.55	$1,094.50