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	$192.52	4.363%	$200.9196	$200.92	$200.90	$200.90
Purchase #2	$52.61	13.339%	$59.6276	$59.63	$59.65	$59.60
Purchase #3	$29.80	4.504%	$31.1422	$31.14	$31.15	$31.10
Purchase #4	$154.77	11.596%	$172.7171	$172.72	$172.70	$172.70
Purchase #5	$139.82	4.456%	$146.0504	$146.05	$146.05	$146.10
Purchase #6	$179.68	13.433%	$203.8164	$203.82	$203.80	$203.80
Purchase #7	$134.87	13.790%	$153.4686	$153.47	$153.45	$153.50
7 purchase totals =	$884.07		$967.7419	$967.75	$967.70	$967.70