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	$73.63	4.784%	$77.1525	$77.15	$77.15	$77.20
Purchase #2	$230.82	8.202%	$249.7519	$249.75	$249.75	$249.80
Purchase #3	$48.45	12.276%	$54.3977	$54.40	$54.40	$54.40
Purchase #4	$242.54	10.698%	$268.4869	$268.49	$268.50	$268.50
Purchase #5	$221.26	11.691%	$247.1275	$247.13	$247.15	$247.10
Purchase #6	$95.69	3.382%	$98.9262	$98.93	$98.95	$98.90
Purchase #7	$18.95	8.707%	$20.6	$20.60	$20.60	$20.60
7 purchase totals =	$931.34		$1,016.4427	$1,016.45	$1,016.50	$1,016.50