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	$191.97	12.780%	$216.5038	$216.50	$216.50	$216.50
Purchase #2	$59.30	10.453%	$65.4986	$65.50	$65.50	$65.50
Purchase #3	$24.58	3.336%	$25.4	$25.40	$25.40	$25.40
Purchase #4	$138.85	5.318%	$146.234	$146.23	$146.25	$146.20
Purchase #5	$154.95	4.367%	$161.7167	$161.72	$161.70	$161.70
Purchase #6	$54.48	13.316%	$61.7346	$61.73	$61.75	$61.70
Purchase #7	$59.76	6.855%	$63.8565	$63.86	$63.85	$63.90
7 purchase totals =	$683.89		$740.9442	$740.94	$740.95	$740.90