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	$33.37	13.735%	$37.9534	$37.95	$37.95	$38.00
Purchase #2	$158.39	4.355%	$165.2879	$165.29	$165.30	$165.30
Purchase #3	$13.26	13.308%	$15.0246	$15.02	$15.00	$15.00
Purchase #4	$159.76	3.592%	$165.4986	$165.50	$165.50	$165.50
Purchase #5	$17.66	9.206%	$19.2858	$19.29	$19.30	$19.30
Purchase #6	$184.36	10.804%	$204.2783	$204.28	$204.30	$204.30
Purchase #7	$173.67	13.335%	$196.8289	$196.83	$196.85	$196.80
7 purchase totals =	$740.47		$804.1575	$804.16	$804.20	$804.20