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	$209.71	11.483%	$233.791	$233.79	$233.80	$233.80
Purchase #2	$231.33	5.471%	$243.9861	$243.99	$244.00	$244.00
Purchase #3	$10.62	9.384%	$11.6166	$11.62	$11.60	$11.60
Purchase #4	$74.31	12.405%	$83.5282	$83.53	$83.55	$83.50
Purchase #5	$13.88	4.396%	$14.4902	$14.49	$14.50	$14.50
Purchase #6	$52.35	5.792%	$55.3821	$55.38	$55.40	$55.40
Purchase #7	$118.42	7.680%	$127.5147	$127.51	$127.50	$127.50
7 purchase totals =	$710.62		$770.3089	$770.31	$770.35	$770.30