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	$137.65	6.395%	$146.4527	$146.45	$146.45	$146.50
Purchase #2	$191.82	10.467%	$211.8978	$211.90	$211.90	$211.90
Purchase #3	$83.88	5.669%	$88.6352	$88.64	$88.65	$88.60
Purchase #4	$138.82	7.163%	$148.7637	$148.76	$148.75	$148.80
Purchase #5	$38.42	3.534%	$39.7778	$39.78	$39.80	$39.80
Purchase #6	$38.65	4.472%	$40.3784	$40.38	$40.40	$40.40
Purchase #7	$36.41	10.563%	$40.256	$40.26	$40.25	$40.30
7 purchase totals =	$665.65		$716.1616	$716.17	$716.20	$716.30