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	$157.27	5.309%	$165.6195	$165.62	$165.60	$165.60
Purchase #2	$57.92	7.133%	$62.0514	$62.05	$62.05	$62.10
Purchase #3	$29.79	4.613%	$31.1642	$31.16	$31.15	$31.20
Purchase #4	$149.64	4.198%	$155.9219	$155.92	$155.90	$155.90
Purchase #5	$158.89	10.154%	$175.0237	$175.02	$175.00	$175.00
Purchase #6	$136.78	8.108%	$147.8701	$147.87	$147.85	$147.90
Purchase #7	$27.43	4.509%	$28.6668	$28.67	$28.65	$28.70
7 purchase totals =	$717.72		$766.3176	$766.31	$766.20	$766.40