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	$158.75	8.261%	$171.8643	$171.86	$171.85	$171.90
Purchase #2	$250.81	11.683%	$280.1121	$280.11	$280.10	$280.10
Purchase #3	$33.92	7.721%	$36.539	$36.54	$36.55	$36.50
Purchase #4	$83.32	3.733%	$86.4303	$86.43	$86.45	$86.40
Purchase #5	$137.78	10.784%	$152.6382	$152.64	$152.65	$152.60
Purchase #6	$184.84	13.448%	$209.6973	$209.70	$209.70	$209.70
Purchase #7	$113.39	4.562%	$118.5629	$118.56	$118.55	$118.60
7 purchase totals =	$962.81		$1,055.8441	$1,055.84	$1,055.85	$1,055.80