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	$142.60	4.256%	$148.6691	$148.67	$148.65	$148.70
Purchase #2	$18.30	9.375%	$20.0156	$20.02	$20.00	$20.00
Purchase #3	$141.59	6.749%	$151.1459	$151.15	$151.15	$151.10
Purchase #4	$123.66	5.692%	$130.6987	$130.70	$130.70	$130.70
Purchase #5	$101.72	11.314%	$113.2286	$113.23	$113.25	$113.20
Purchase #6	$113.26	12.329%	$127.2238	$127.22	$127.20	$127.20
Purchase #7	$49.47	5.609%	$52.2448	$52.24	$52.25	$52.20
7 purchase totals =	$690.60		$743.2265	$743.23	$743.20	$743.10