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	$54.52	3.192%	$56.2603	$56.26	$56.25	$56.30
Purchase #2	$61.97	5.318%	$65.2656	$65.27	$65.25	$65.30
Purchase #3	$51.43	7.364%	$55.2173	$55.22	$55.20	$55.20
Purchase #4	$203.30	9.651%	$222.9205	$222.92	$222.90	$222.90
Purchase #5	$222.87	9.108%	$243.169	$243.17	$243.15	$243.20
Purchase #6	$244.57	12.477%	$275.085	$275.09	$275.10	$275.10
Purchase #7	$46.29	6.829%	$49.4511	$49.45	$49.45	$49.50
7 purchase totals =	$884.95		$967.3688	$967.38	$967.30	$967.50