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	$216.43	6.350%	$230.1733	$230.17	$230.15	$230.20
Purchase #2	$249.87	8.728%	$271.6787	$271.68	$271.70	$271.70
Purchase #3	$18.94	12.677%	$21.341	$21.34	$21.35	$21.30
Purchase #4	$71.59	11.753%	$80.004	$80.00	$80.00	$80.00
Purchase #5	$186.38	12.723%	$210.0931	$210.09	$210.10	$210.10
Purchase #6	$140.54	7.538%	$151.1339	$151.13	$151.15	$151.10
Purchase #7	$120.46	6.201%	$127.9297	$127.93	$127.95	$127.90
7 purchase totals =	$1,004.21		$1,092.3537	$1,092.34	$1,092.40	$1,092.30