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	$164.59	5.388%	$173.4581	$173.46	$173.45	$173.50
Purchase #2	$174.27	5.535%	$183.9158	$183.92	$183.90	$183.90
Purchase #3	$63.31	12.482%	$71.2124	$71.21	$71.20	$71.20
Purchase #4	$123.48	8.679%	$134.1968	$134.20	$134.20	$134.20
Purchase #5	$91.28	8.814%	$99.3254	$99.33	$99.35	$99.30
Purchase #6	$15.82	11.220%	$17.595	$17.60	$17.60	$17.60
Purchase #7	$140.65	7.475%	$151.1636	$151.16	$151.15	$151.20
7 purchase totals =	$773.40		$830.8671	$830.88	$830.85	$830.90