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	$101.37	9.704%	$111.2069	$111.21	$111.20	$111.20
Purchase #2	$105.46	11.664%	$117.7609	$117.76	$117.75	$117.80
Purchase #3	$28.26	3.840%	$29.3452	$29.35	$29.35	$29.30
Purchase #4	$169.40	11.382%	$188.6811	$188.68	$188.70	$188.70
Purchase #5	$127.88	9.114%	$139.535	$139.54	$139.55	$139.50
Purchase #6	$220.79	10.156%	$243.2134	$243.21	$243.20	$243.20
Purchase #7	$173.41	3.307%	$179.1447	$179.14	$179.15	$179.10
7 purchase totals =	$926.57		$1,008.8872	$1,008.89	$1,008.90	$1,008.80