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	$153.60	4.377%	$160.3231	$160.32	$160.30	$160.30
Purchase #2	$144.62	5.567%	$152.671	$152.67	$152.65	$152.70
Purchase #3	$91.58	8.799%	$99.6381	$99.64	$99.65	$99.60
Purchase #4	$235.92	4.327%	$246.1283	$246.13	$246.15	$246.10
Purchase #5	$123.78	5.365%	$130.4208	$130.42	$130.40	$130.40
Purchase #6	$203.95	12.671%	$229.7925	$229.79	$229.80	$229.80
Purchase #7	$29.35	10.323%	$32.3798	$32.38	$32.40	$32.40
7 purchase totals =	$982.80		$1,051.3536	$1,051.35	$1,051.35	$1,051.30