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	$193.35	12.490%	$217.4994	$217.50	$217.50	$217.50
Purchase #2	$42.74	13.379%	$48.4582	$48.46	$48.45	$48.50
Purchase #3	$123.47	3.853%	$128.2273	$128.23	$128.25	$128.20
Purchase #4	$101.48	9.608%	$111.2302	$111.23	$111.25	$111.20
Purchase #5	$74.87	6.121%	$79.4528	$79.45	$79.45	$79.50
Purchase #6	$78.85	9.392%	$86.2556	$86.26	$86.25	$86.30
Purchase #7	$92.77	8.618%	$100.7649	$100.76	$100.75	$100.80
7 purchase totals =	$707.53		$771.8884	$771.89	$771.90	$772.00