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	$244.46	7.539%	$262.8898	$262.89	$262.90	$262.90
Purchase #2	$42.96	5.748%	$45.4293	$45.43	$45.45	$45.40
Purchase #3	$70.29	8.561%	$76.3075	$76.31	$76.30	$76.30
Purchase #4	$193.74	6.412%	$206.1626	$206.16	$206.15	$206.20
Purchase #5	$94.27	7.729%	$101.5561	$101.56	$101.55	$101.60
Purchase #6	$104.83	4.103%	$109.1312	$109.13	$109.15	$109.10
Purchase #7	$181.42	4.846%	$190.2116	$190.21	$190.20	$190.20
7 purchase totals =	$931.97		$991.6881	$991.69	$991.70	$991.70