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	$44.47	13.121%	$50.3049	$50.30	$50.30	$50.30
Purchase #2	$32.74	9.108%	$35.722	$35.72	$35.70	$35.70
Purchase #3	$140.44	3.706%	$145.6447	$145.64	$145.65	$145.60
Purchase #4	$143.59	5.572%	$151.5908	$151.59	$151.60	$151.60
Purchase #5	$153.62	4.712%	$160.8586	$160.86	$160.85	$160.90
Purchase #6	$235.27	6.759%	$251.1719	$251.17	$251.15	$251.20
Purchase #7	$211.40	10.325%	$233.2271	$233.23	$233.25	$233.20
7 purchase totals =	$961.53		$1,028.5200	$1,028.51	$1,028.50	$1,028.50