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	$99.67	4.102%	$103.7585	$103.76	$103.75	$103.80
Purchase #2	$233.41	8.514%	$253.2825	$253.28	$253.30	$253.30
Purchase #3	$197.48	10.151%	$217.5262	$217.53	$217.55	$217.50
Purchase #4	$146.40	13.643%	$166.3734	$166.37	$166.35	$166.40
Purchase #5	$149.55	9.694%	$164.0474	$164.05	$164.05	$164.00
Purchase #6	$137.63	13.536%	$156.2596	$156.26	$156.25	$156.30
Purchase #7	$129.43	7.765%	$139.4802	$139.48	$139.50	$139.50
7 purchase totals =	$1,093.57		$1,200.7278	$1,200.73	$1,200.75	$1,200.80