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	$124.74	6.841%	$133.2735	$133.27	$133.25	$133.30
Purchase #2	$79.99	13.251%	$90.5895	$90.59	$90.60	$90.60
Purchase #3	$127.75	3.560%	$132.2979	$132.30	$132.30	$132.30
Purchase #4	$225.88	13.799%	$257.0492	$257.05	$257.05	$257.00
Purchase #5	$95.91	9.658%	$105.173	$105.17	$105.15	$105.20
Purchase #6	$113.50	12.160%	$127.3016	$127.30	$127.30	$127.30
Purchase #7	$54.28	13.736%	$61.7359	$61.74	$61.75	$61.70
7 purchase totals =	$822.05		$907.4206	$907.42	$907.40	$907.40