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	$152.40	13.296%	$172.6631	$172.66	$172.65	$172.70
Purchase #2	$219.63	6.872%	$234.723	$234.72	$234.70	$234.70
Purchase #3	$54.48	7.530%	$58.5823	$58.58	$58.60	$58.60
Purchase #4	$70.52	9.502%	$77.2208	$77.22	$77.20	$77.20
Purchase #5	$33.66	11.541%	$37.5447	$37.54	$37.55	$37.50
Purchase #6	$46.69	3.844%	$48.4848	$48.48	$48.50	$48.50
Purchase #7	$212.30	4.532%	$221.9214	$221.92	$221.90	$221.90
7 purchase totals =	$789.68		$851.1401	$851.12	$851.10	$851.10