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	$41.89	13.686%	$47.6231	$47.62	$47.60	$47.60
Purchase #2	$75.25	10.672%	$83.2807	$83.28	$83.30	$83.30
Purchase #3	$146.59	10.367%	$161.787	$161.79	$161.80	$161.80
Purchase #4	$19.43	4.391%	$20.2832	$20.28	$20.30	$20.30
Purchase #5	$96.73	3.548%	$100.162	$100.16	$100.15	$100.20
Purchase #6	$151.36	3.538%	$156.7151	$156.72	$156.70	$156.70
Purchase #7	$54.29	6.240%	$57.6777	$57.68	$57.70	$57.70
7 purchase totals =	$585.54		$627.5288	$627.53	$627.55	$627.60