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	$77.33	7.857%	$83.4058	$83.41	$83.40	$83.40
Purchase #2	$191.28	3.657%	$198.2751	$198.28	$198.30	$198.30
Purchase #3	$230.66	10.649%	$255.223	$255.22	$255.20	$255.20
Purchase #4	$137.87	9.676%	$151.2103	$151.21	$151.20	$151.20
Purchase #5	$73.87	10.586%	$81.6899	$81.69	$81.70	$81.70
Purchase #6	$29.29	9.744%	$32.144	$32.14	$32.15	$32.10
Purchase #7	$74.58	10.508%	$82.4169	$82.42	$82.40	$82.40
7 purchase totals =	$814.88		$884.3650	$884.37	$884.35	$884.30