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	$214.90	6.806%	$229.5261	$229.53	$229.55	$229.50
Purchase #2	$53.32	3.485%	$55.1782	$55.18	$55.20	$55.20
Purchase #3	$37.67	6.782%	$40.2248	$40.22	$40.20	$40.20
Purchase #4	$49.85	4.136%	$51.9118	$51.91	$51.90	$51.90
Purchase #5	$156.72	3.138%	$161.6379	$161.64	$161.65	$161.60
Purchase #6	$79.63	7.707%	$85.7671	$85.77	$85.75	$85.80
Purchase #7	$135.84	9.207%	$148.3468	$148.35	$148.35	$148.30
7 purchase totals =	$727.93		$772.5927	$772.60	$772.60	$772.50