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	$231.43	10.396%	$255.4895	$255.49	$255.50	$255.50
Purchase #2	$146.28	3.756%	$151.7743	$151.77	$151.75	$151.80
Purchase #3	$130.49	11.484%	$145.4755	$145.48	$145.50	$145.50
Purchase #4	$121.32	5.436%	$127.915	$127.92	$127.90	$127.90
Purchase #5	$222.85	8.254%	$241.244	$241.24	$241.25	$241.20
Purchase #6	$190.36	11.489%	$212.2305	$212.23	$212.25	$212.20
Purchase #7	$243.82	12.841%	$275.1289	$275.13	$275.15	$275.10
7 purchase totals =	$1,286.55		$1,409.2577	$1,409.26	$1,409.30	$1,409.20