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	$168.95	12.728%	$190.454	$190.45	$190.45	$190.50
Purchase #2	$138.44	13.363%	$156.9397	$156.94	$156.95	$156.90
Purchase #3	$96.68	8.297%	$104.7015	$104.70	$104.70	$104.70
Purchase #4	$191.49	10.468%	$211.5352	$211.54	$211.55	$211.50
Purchase #5	$113.82	11.739%	$127.1813	$127.18	$127.20	$127.20
Purchase #6	$135.71	13.718%	$154.3267	$154.33	$154.35	$154.30
Purchase #7	$55.78	12.689%	$62.8579	$62.86	$62.85	$62.90
7 purchase totals =	$900.87		$1,007.9963	$1,008.00	$1,008.05	$1,008.00