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	$93.76	12.394%	$105.3806	$105.38	$105.40	$105.40
Purchase #2	$240.59	5.781%	$254.4985	$254.50	$254.50	$254.50
Purchase #3	$128.37	9.320%	$140.3341	$140.33	$140.35	$140.30
Purchase #4	$74.61	4.301%	$77.819	$77.82	$77.80	$77.80
Purchase #5	$11.34	3.703%	$11.7599	$11.76	$11.75	$11.80
Purchase #6	$160.80	4.522%	$168.0714	$168.07	$168.05	$168.10
Purchase #7	$68.93	11.114%	$76.5909	$76.59	$76.60	$76.60
7 purchase totals =	$778.40		$834.4544	$834.45	$834.45	$834.50