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	$56.27	7.449%	$60.4616	$60.46	$60.45	$60.50
Purchase #2	$65.82	11.645%	$73.4847	$73.48	$73.50	$73.50
Purchase #3	$78.57	6.535%	$83.7045	$83.70	$83.70	$83.70
Purchase #4	$22.27	4.528%	$23.2784	$23.28	$23.30	$23.30
Purchase #5	$88.91	7.153%	$95.2697	$95.27	$95.25	$95.30
Purchase #6	$55.81	5.246%	$58.7378	$58.74	$58.75	$58.70
Purchase #7	$224.62	13.728%	$255.4558	$255.46	$255.45	$255.50
7 purchase totals =	$592.27		$650.3925	$650.39	$650.40	$650.50