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	$61.26	10.246%	$67.5367	$67.54	$67.55	$67.50
Purchase #2	$12.86	7.623%	$13.8403	$13.84	$13.85	$13.80
Purchase #3	$67.59	5.548%	$71.3399	$71.34	$71.35	$71.30
Purchase #4	$33.84	7.786%	$36.4748	$36.47	$36.45	$36.50
Purchase #5	$176.87	10.379%	$195.2273	$195.23	$195.25	$195.20
Purchase #6	$83.45	8.613%	$90.6375	$90.64	$90.65	$90.60
Purchase #7	$141.49	12.429%	$159.0758	$159.08	$159.10	$159.10
7 purchase totals =	$577.36		$634.1323	$634.14	$634.20	$634.00