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	$159.60	10.160%	$175.8154	$175.82	$175.80	$175.80
Purchase #2	$209.91	3.117%	$216.4529	$216.45	$216.45	$216.50
Purchase #3	$106.65	13.146%	$120.6702	$120.67	$120.65	$120.70
Purchase #4	$32.89	13.685%	$37.391	$37.39	$37.40	$37.40
Purchase #5	$144.82	11.331%	$161.2296	$161.23	$161.25	$161.20
Purchase #6	$32.88	13.470%	$37.3089	$37.31	$37.30	$37.30
Purchase #7	$132.97	9.235%	$145.2498	$145.25	$145.25	$145.20
7 purchase totals =	$819.72		$894.1178	$894.12	$894.10	$894.10