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	$102.83	9.531%	$112.6307	$112.63	$112.65	$112.60
Purchase #2	$186.65	12.595%	$210.1586	$210.16	$210.15	$210.20
Purchase #3	$37.56	4.538%	$39.2645	$39.26	$39.25	$39.30
Purchase #4	$66.99	7.500%	$72.0143	$72.01	$72.00	$72.00
Purchase #5	$118.48	7.548%	$127.4229	$127.42	$127.40	$127.40
Purchase #6	$165.54	4.862%	$173.5886	$173.59	$173.60	$173.60
Purchase #7	$68.85	11.870%	$77.0225	$77.02	$77.00	$77.00
7 purchase totals =	$746.90		$812.1021	$812.09	$812.05	$812.10