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	$74.95	5.222%	$78.8639	$78.86	$78.85	$78.90
Purchase #2	$33.29	9.707%	$36.5215	$36.52	$36.50	$36.50
Purchase #3	$142.30	9.717%	$156.1273	$156.13	$156.15	$156.10
Purchase #4	$76.85	6.287%	$81.6816	$81.68	$81.70	$81.70
Purchase #5	$55.69	12.281%	$62.5293	$62.53	$62.55	$62.50
Purchase #6	$45.42	4.350%	$47.3958	$47.40	$47.40	$47.40
Purchase #7	$146.54	11.142%	$162.8675	$162.87	$162.85	$162.90
7 purchase totals =	$575.04		$625.9869	$625.99	$626.00	$626.00