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	$67.72	4.177%	$70.5487	$70.55	$70.55	$70.50
Purchase #2	$18.78	7.538%	$20.1956	$20.20	$20.20	$20.20
Purchase #3	$11.45	5.598%	$12.091	$12.09	$12.10	$12.10
Purchase #4	$229.74	12.679%	$258.8687	$258.87	$258.85	$258.90
Purchase #5	$208.49	6.535%	$222.1148	$222.11	$222.10	$222.10
Purchase #6	$67.31	4.648%	$70.4386	$70.44	$70.45	$70.40
Purchase #7	$112.30	13.154%	$127.0719	$127.07	$127.05	$127.10
7 purchase totals =	$715.79		$781.3293	$781.33	$781.30	$781.30