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	$118.69	5.227%	$124.8939	$124.89	$124.90	$124.90
Purchase #2	$33.50	11.123%	$37.2262	$37.23	$37.25	$37.20
Purchase #3	$65.66	13.792%	$74.7158	$74.72	$74.70	$74.70
Purchase #4	$158.81	10.147%	$174.9245	$174.92	$174.90	$174.90
Purchase #5	$50.42	7.245%	$54.0729	$54.07	$54.05	$54.10
Purchase #6	$64.30	12.496%	$72.3349	$72.33	$72.35	$72.30
Purchase #7	$71.47	3.182%	$73.7442	$73.74	$73.75	$73.70
7 purchase totals =	$562.85		$611.9124	$611.90	$611.90	$611.80