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	$173.99	4.550%	$181.9065	$181.91	$181.90	$181.90
Purchase #2	$43.79	13.405%	$49.66	$49.66	$49.65	$49.70
Purchase #3	$154.32	8.723%	$167.7813	$167.78	$167.80	$167.80
Purchase #4	$105.27	3.823%	$109.2945	$109.29	$109.30	$109.30
Purchase #5	$143.72	6.150%	$152.5588	$152.56	$152.55	$152.60
Purchase #6	$30.45	5.328%	$32.0724	$32.07	$32.05	$32.10
Purchase #7	$244.45	7.243%	$262.1555	$262.16	$262.15	$262.20
7 purchase totals =	$895.99		$955.4290	$955.43	$955.40	$955.60