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	$143.54	7.168%	$153.8289	$153.83	$153.85	$153.80
Purchase #2	$68.75	13.562%	$78.0739	$78.07	$78.05	$78.10
Purchase #3	$112.58	13.497%	$127.7749	$127.77	$127.75	$127.80
Purchase #4	$165.72	7.151%	$177.5706	$177.57	$177.55	$177.60
Purchase #5	$9.49	12.172%	$10.6451	$10.65	$10.65	$10.60
Purchase #6	$157.56	7.156%	$168.835	$168.84	$168.85	$168.80
Purchase #7	$180.30	8.403%	$195.4506	$195.45	$195.45	$195.50
7 purchase totals =	$837.94		$912.1790	$912.18	$912.15	$912.20