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	$197.83	13.802%	$225.1345	$225.13	$225.15	$225.10
Purchase #2	$59.72	9.816%	$65.5821	$65.58	$65.60	$65.60
Purchase #3	$101.54	7.498%	$109.1535	$109.15	$109.15	$109.20
Purchase #4	$159.74	8.707%	$173.6486	$173.65	$173.65	$173.60
Purchase #5	$121.40	5.302%	$127.8366	$127.84	$127.85	$127.80
Purchase #6	$215.58	4.193%	$224.6193	$224.62	$224.60	$224.60
Purchase #7	$45.67	5.713%	$48.2791	$48.28	$48.30	$48.30
7 purchase totals =	$901.48		$974.2537	$974.25	$974.30	$974.20