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	$90.65	9.544%	$99.3016	$99.30	$99.30	$99.30
Purchase #2	$20.95	8.715%	$22.7758	$22.78	$22.80	$22.80
Purchase #3	$10.62	3.315%	$10.9721	$10.97	$10.95	$11.00
Purchase #4	$150.79	10.491%	$166.6094	$166.61	$166.60	$166.60
Purchase #5	$228.49	12.259%	$256.5006	$256.50	$256.50	$256.50
Purchase #6	$94.47	10.426%	$104.3194	$104.32	$104.30	$104.30
Purchase #7	$86.92	6.698%	$92.7419	$92.74	$92.75	$92.70
7 purchase totals =	$682.89		$753.2208	$753.22	$753.20	$753.20