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	$202.37	11.115%	$224.8634	$224.86	$224.85	$224.90
Purchase #2	$16.83	10.435%	$18.5862	$18.59	$18.60	$18.60
Purchase #3	$88.27	5.677%	$93.2811	$93.28	$93.30	$93.30
Purchase #4	$233.89	12.285%	$262.6234	$262.62	$262.60	$262.60
Purchase #5	$89.46	3.431%	$92.5294	$92.53	$92.55	$92.50
Purchase #6	$189.95	4.841%	$199.1455	$199.15	$199.15	$199.10
Purchase #7	$147.35	7.462%	$158.3453	$158.35	$158.35	$158.30
7 purchase totals =	$968.12		$1,049.3743	$1,049.38	$1,049.40	$1,049.30