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	$126.40	6.405%	$134.4959	$134.50	$134.50	$134.50
Purchase #2	$70.65	10.792%	$78.2745	$78.27	$78.25	$78.30
Purchase #3	$165.30	4.489%	$172.7203	$172.72	$172.70	$172.70
Purchase #4	$99.37	6.497%	$105.8261	$105.83	$105.85	$105.80
Purchase #5	$211.97	4.255%	$220.9893	$220.99	$221.00	$221.00
Purchase #6	$45.28	7.258%	$48.5664	$48.57	$48.55	$48.60
Purchase #7	$240.90	7.248%	$258.3604	$258.36	$258.35	$258.40
7 purchase totals =	$959.87		$1,019.2329	$1,019.24	$1,019.20	$1,019.30