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	$59.34	13.635%	$67.431	$67.43	$67.45	$67.40
Purchase #2	$195.57	6.560%	$208.3994	$208.40	$208.40	$208.40
Purchase #3	$47.58	4.128%	$49.5441	$49.54	$49.55	$49.50
Purchase #4	$171.40	9.530%	$187.7344	$187.73	$187.75	$187.70
Purchase #5	$142.55	11.204%	$158.5213	$158.52	$158.50	$158.50
Purchase #6	$159.43	12.555%	$179.4464	$179.45	$179.45	$179.40
Purchase #7	$246.58	12.128%	$276.4852	$276.49	$276.50	$276.50
7 purchase totals =	$1,022.45		$1,127.5618	$1,127.56	$1,127.60	$1,127.40