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	$174.95	12.251%	$196.3831	$196.38	$196.40	$196.40
Purchase #2	$205.29	5.176%	$215.9158	$215.92	$215.90	$215.90
Purchase #3	$23.89	7.720%	$25.7343	$25.73	$25.75	$25.70
Purchase #4	$152.71	13.510%	$173.3411	$173.34	$173.35	$173.30
Purchase #5	$175.30	9.468%	$191.8974	$191.90	$191.90	$191.90
Purchase #6	$226.90	7.767%	$244.5233	$244.52	$244.50	$244.50
Purchase #7	$209.37	13.107%	$236.8121	$236.81	$236.80	$236.80
7 purchase totals =	$1,168.41		$1,284.6071	$1,284.60	$1,284.60	$1,284.50