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	$101.66	4.158%	$105.887	$105.89	$105.90	$105.90
Purchase #2	$35.39	12.718%	$39.8909	$39.89	$39.90	$39.90
Purchase #3	$178.61	6.191%	$189.6677	$189.67	$189.65	$189.70
Purchase #4	$60.32	5.668%	$63.7389	$63.74	$63.75	$63.70
Purchase #5	$148.81	3.408%	$153.8814	$153.88	$153.90	$153.90
Purchase #6	$41.57	11.837%	$46.4906	$46.49	$46.50	$46.50
Purchase #7	$165.60	9.394%	$181.1565	$181.16	$181.15	$181.20
7 purchase totals =	$731.96		$780.7130	$780.72	$780.75	$780.80