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	$225.63	4.729%	$236.3	$236.30	$236.30	$236.30
Purchase #2	$143.36	7.508%	$154.1235	$154.12	$154.10	$154.10
Purchase #3	$182.72	4.384%	$190.7304	$190.73	$190.75	$190.70
Purchase #4	$138.36	9.823%	$151.9511	$151.95	$151.95	$152.00
Purchase #5	$205.68	6.217%	$218.4671	$218.47	$218.45	$218.50
Purchase #6	$56.51	5.472%	$59.6022	$59.60	$59.60	$59.60
Purchase #7	$58.33	3.711%	$60.4946	$60.49	$60.50	$60.50
7 purchase totals =	$1,010.59		$1,071.6689	$1,071.66	$1,071.65	$1,071.70