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	$92.97	9.753%	$102.0374	$102.04	$102.05	$102.00
Purchase #2	$94.26	10.672%	$104.3194	$104.32	$104.30	$104.30
Purchase #3	$171.71	3.341%	$177.4468	$177.45	$177.45	$177.40
Purchase #4	$242.87	4.658%	$254.1829	$254.18	$254.20	$254.20
Purchase #5	$214.52	13.510%	$243.5017	$243.50	$243.50	$243.50
Purchase #6	$164.79	5.309%	$173.5387	$173.54	$173.55	$173.50
Purchase #7	$90.66	4.768%	$94.9827	$94.98	$95.00	$95.00
7 purchase totals =	$1,071.78		$1,150.0096	$1,150.01	$1,150.05	$1,149.90