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	$116.31	6.162%	$123.477	$123.48	$123.50	$123.50
Purchase #2	$157.67	13.601%	$179.1147	$179.11	$179.10	$179.10
Purchase #3	$185.55	11.204%	$206.339	$206.34	$206.35	$206.30
Purchase #4	$101.26	4.196%	$105.5089	$105.51	$105.50	$105.50
Purchase #5	$190.54	7.759%	$205.324	$205.32	$205.30	$205.30
Purchase #6	$244.80	4.455%	$255.7058	$255.71	$255.70	$255.70
Purchase #7	$230.83	3.664%	$239.2876	$239.29	$239.30	$239.30
7 purchase totals =	$1,226.96		$1,314.7570	$1,314.76	$1,314.75	$1,314.70