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	$141.89	3.282%	$146.5468	$146.55	$146.55	$146.50
Purchase #2	$216.39	6.322%	$230.0702	$230.07	$230.05	$230.10
Purchase #3	$244.61	7.813%	$263.7214	$263.72	$263.70	$263.70
Purchase #4	$112.47	12.823%	$126.892	$126.89	$126.90	$126.90
Purchase #5	$234.30	13.117%	$265.0331	$265.03	$265.05	$265.00
Purchase #6	$64.45	9.203%	$70.3813	$70.38	$70.40	$70.40
Purchase #7	$108.53	3.103%	$111.8977	$111.90	$111.90	$111.90
7 purchase totals =	$1,122.64		$1,214.5425	$1,214.54	$1,214.55	$1,214.50