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	$144.39	10.620%	$159.7242	$159.72	$159.70	$159.70
Purchase #2	$122.82	3.116%	$126.6471	$126.65	$126.65	$126.60
Purchase #3	$146.35	13.241%	$165.7282	$165.73	$165.75	$165.70
Purchase #4	$91.56	4.769%	$95.9265	$95.93	$95.95	$95.90
Purchase #5	$173.48	13.340%	$196.6222	$196.62	$196.60	$196.60
Purchase #6	$230.30	12.827%	$259.8406	$259.84	$259.85	$259.80
Purchase #7	$50.63	5.442%	$53.3853	$53.39	$53.40	$53.40
7 purchase totals =	$959.53		$1,057.8741	$1,057.88	$1,057.90	$1,057.70