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	$47.83	11.371%	$53.2687	$53.27	$53.25	$53.30
Purchase #2	$74.38	8.719%	$80.8652	$80.87	$80.85	$80.90
Purchase #3	$108.55	13.462%	$123.163	$123.16	$123.15	$123.20
Purchase #4	$33.92	10.235%	$37.3917	$37.39	$37.40	$37.40
Purchase #5	$164.56	3.438%	$170.2176	$170.22	$170.20	$170.20
Purchase #6	$105.58	6.414%	$112.3519	$112.35	$112.35	$112.40
Purchase #7	$89.78	12.236%	$100.7655	$100.77	$100.75	$100.80
7 purchase totals =	$624.60		$678.0236	$678.03	$677.95	$678.20