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	$231.73	5.641%	$244.8019	$244.80	$244.80	$244.80
Purchase #2	$181.72	4.749%	$190.3499	$190.35	$190.35	$190.30
Purchase #3	$159.72	8.251%	$172.8985	$172.90	$172.90	$172.90
Purchase #4	$24.44	12.806%	$27.5698	$27.57	$27.55	$27.60
Purchase #5	$214.52	9.295%	$234.4596	$234.46	$234.45	$234.50
Purchase #6	$159.83	8.529%	$173.4619	$173.46	$173.45	$173.50
Purchase #7	$141.93	11.231%	$157.8702	$157.87	$157.85	$157.90
7 purchase totals =	$1,113.89		$1,201.4118	$1,201.41	$1,201.35	$1,201.50