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	$94.38	11.671%	$105.3951	$105.40	$105.40	$105.40
Purchase #2	$61.45	11.318%	$68.4049	$68.40	$68.40	$68.40
Purchase #3	$135.78	7.510%	$145.9771	$145.98	$146.00	$146.00
Purchase #4	$48.74	3.668%	$50.5278	$50.53	$50.55	$50.50
Purchase #5	$158.41	4.730%	$165.9028	$165.90	$165.90	$165.90
Purchase #6	$53.52	7.571%	$57.572	$57.57	$57.55	$57.60
Purchase #7	$137.74	4.277%	$143.6311	$143.63	$143.65	$143.60
7 purchase totals =	$690.02		$737.4108	$737.41	$737.45	$737.40