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	$12.74	12.146%	$14.2874	$14.29	$14.30	$14.30
Purchase #2	$164.96	6.148%	$175.1017	$175.10	$175.10	$175.10
Purchase #3	$34.90	7.621%	$37.5597	$37.56	$37.55	$37.60
Purchase #4	$150.64	5.364%	$158.7203	$158.72	$158.70	$158.70
Purchase #5	$229.32	12.563%	$258.1295	$258.13	$258.15	$258.10
Purchase #6	$148.58	13.260%	$168.2817	$168.28	$168.30	$168.30
Purchase #7	$26.69	6.211%	$28.3477	$28.35	$28.35	$28.30
7 purchase totals =	$767.83		$840.4280	$840.43	$840.45	$840.40