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	$22.83	6.315%	$24.2717	$24.27	$24.25	$24.30
Purchase #2	$88.39	12.504%	$99.4423	$99.44	$99.45	$99.40
Purchase #3	$63.69	13.580%	$72.3391	$72.34	$72.35	$72.30
Purchase #4	$222.95	4.550%	$233.0942	$233.09	$233.10	$233.10
Purchase #5	$153.72	5.407%	$162.0316	$162.03	$162.05	$162.00
Purchase #6	$151.28	4.244%	$157.7003	$157.70	$157.70	$157.70
Purchase #7	$141.80	10.219%	$156.2905	$156.29	$156.30	$156.30
7 purchase totals =	$844.66		$905.1697	$905.16	$905.20	$905.10