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	$20.36	9.488%	$22.2918	$22.29	$22.30	$22.30
Purchase #2	$183.97	5.709%	$194.4728	$194.47	$194.45	$194.50
Purchase #3	$12.86	3.211%	$13.2729	$13.27	$13.25	$13.30
Purchase #4	$54.57	5.400%	$57.5168	$57.52	$57.50	$57.50
Purchase #5	$115.49	10.435%	$127.5414	$127.54	$127.55	$127.50
Purchase #6	$18.31	12.554%	$20.6086	$20.61	$20.60	$20.60
Purchase #7	$165.88	13.571%	$188.3916	$188.39	$188.40	$188.40
7 purchase totals =	$571.44		$624.0959	$624.09	$624.05	$624.10