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	$101.60	10.728%	$112.4996	$112.50	$112.50	$112.50
Purchase #2	$33.61	9.792%	$36.9011	$36.90	$36.90	$36.90
Purchase #3	$195.85	4.593%	$204.8454	$204.85	$204.85	$204.80
Purchase #4	$99.34	12.634%	$111.8906	$111.89	$111.90	$111.90
Purchase #5	$171.29	5.768%	$181.17	$181.17	$181.15	$181.20
Purchase #6	$114.62	8.456%	$124.3123	$124.31	$124.30	$124.30
Purchase #7	$217.65	8.303%	$235.7215	$235.72	$235.70	$235.70
7 purchase totals =	$933.96		$1,007.3405	$1,007.34	$1,007.30	$1,007.30