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	$39.60	12.110%	$44.3956	$44.40	$44.40	$44.40
Purchase #2	$126.68	13.842%	$144.215	$144.22	$144.20	$144.20
Purchase #3	$226.65	12.279%	$254.4804	$254.48	$254.50	$254.50
Purchase #4	$109.38	5.172%	$115.0371	$115.04	$115.05	$115.00
Purchase #5	$116.64	9.518%	$127.7418	$127.74	$127.75	$127.70
Purchase #6	$191.55	4.609%	$200.3785	$200.38	$200.40	$200.40
Purchase #7	$250.86	9.341%	$274.2928	$274.29	$274.30	$274.30
7 purchase totals =	$1,061.36		$1,160.5412	$1,160.55	$1,160.60	$1,160.50