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	$64.27	11.793%	$71.8494	$71.85	$71.85	$71.80
Purchase #2	$106.82	8.643%	$116.0525	$116.05	$116.05	$116.10
Purchase #3	$175.61	9.838%	$192.8865	$192.89	$192.90	$192.90
Purchase #4	$82.25	12.634%	$92.6415	$92.64	$92.65	$92.60
Purchase #5	$122.94	6.578%	$131.027	$131.03	$131.05	$131.00
Purchase #6	$65.25	10.654%	$72.2017	$72.20	$72.20	$72.20
Purchase #7	$187.90	10.723%	$208.0485	$208.05	$208.05	$208.00
7 purchase totals =	$805.04		$884.7071	$884.71	$884.75	$884.60