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	$153.68	12.282%	$172.555	$172.56	$172.55	$172.60
Purchase #2	$58.99	3.500%	$61.0547	$61.05	$61.05	$61.10
Purchase #3	$38.28	6.369%	$40.7181	$40.72	$40.70	$40.70
Purchase #4	$175.64	6.107%	$186.3663	$186.37	$186.35	$186.40
Purchase #5	$102.25	9.380%	$111.8411	$111.84	$111.85	$111.80
Purchase #6	$155.33	10.296%	$171.3228	$171.32	$171.30	$171.30
Purchase #7	$121.46	7.164%	$130.1614	$130.16	$130.15	$130.20
7 purchase totals =	$805.63		$874.0194	$874.02	$873.95	$874.10