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	$62.97	13.414%	$71.4168	$71.42	$71.40	$71.40
Purchase #2	$179.52	12.685%	$202.2921	$202.29	$202.30	$202.30
Purchase #3	$143.47	3.361%	$148.292	$148.29	$148.30	$148.30
Purchase #4	$28.41	8.690%	$30.8788	$30.88	$30.90	$30.90
Purchase #5	$29.42	10.368%	$32.4703	$32.47	$32.45	$32.50
Purchase #6	$53.96	10.204%	$59.4661	$59.47	$59.45	$59.50
Purchase #7	$153.49	11.196%	$170.6747	$170.67	$170.65	$170.70
7 purchase totals =	$651.24		$715.4908	$715.49	$715.45	$715.60