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	$92.73	12.161%	$104.0069	$104.01	$104.00	$104.00
Purchase #2	$28.64	11.839%	$32.0307	$32.03	$32.05	$32.00
Purchase #3	$172.48	9.194%	$188.3378	$188.34	$188.35	$188.30
Purchase #4	$214.47	13.322%	$243.0417	$243.04	$243.05	$243.00
Purchase #5	$37.80	8.212%	$40.9041	$40.90	$40.90	$40.90
Purchase #6	$130.55	8.309%	$141.3974	$141.40	$141.40	$141.40
Purchase #7	$105.81	5.363%	$111.4846	$111.48	$111.50	$111.50
7 purchase totals =	$782.48		$861.2032	$861.20	$861.25	$861.10