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	$235.47	5.816%	$249.1649	$249.16	$249.15	$249.20
Purchase #2	$142.82	10.240%	$157.4448	$157.44	$157.45	$157.40
Purchase #3	$31.68	3.338%	$32.7375	$32.74	$32.75	$32.70
Purchase #4	$239.85	6.422%	$255.2532	$255.25	$255.25	$255.30
Purchase #5	$63.45	12.627%	$71.4618	$71.46	$71.45	$71.50
Purchase #6	$250.70	7.813%	$270.2872	$270.29	$270.30	$270.30
Purchase #7	$31.94	9.318%	$34.9162	$34.92	$34.90	$34.90
7 purchase totals =	$995.91		$1,071.2656	$1,071.26	$1,071.25	$1,071.30