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	$246.55	10.152%	$271.5798	$271.58	$271.60	$271.60
Purchase #2	$143.83	3.574%	$148.9705	$148.97	$148.95	$149.00
Purchase #3	$11.58	11.168%	$12.8733	$12.87	$12.85	$12.90
Purchase #4	$191.37	10.436%	$211.3414	$211.34	$211.35	$211.30
Purchase #5	$183.35	4.449%	$191.5072	$191.51	$191.50	$191.50
Purchase #6	$108.63	5.420%	$114.5177	$114.52	$114.50	$114.50
Purchase #7	$98.61	11.860%	$110.3051	$110.31	$110.30	$110.30
7 purchase totals =	$983.92		$1,061.0950	$1,061.10	$1,061.05	$1,061.10