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	$151.90	9.756%	$166.7194	$166.72	$166.70	$166.70
Purchase #2	$68.78	3.472%	$71.168	$71.17	$71.15	$71.20
Purchase #3	$197.62	10.161%	$217.7002	$217.70	$217.70	$217.70
Purchase #4	$105.98	10.507%	$117.1153	$117.12	$117.10	$117.10
Purchase #5	$70.72	10.686%	$78.2771	$78.28	$78.30	$78.30
Purchase #6	$230.36	10.706%	$255.0223	$255.02	$255.00	$255.00
Purchase #7	$27.93	5.169%	$29.3737	$29.37	$29.35	$29.40
7 purchase totals =	$853.29		$935.3760	$935.38	$935.30	$935.40