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	$160.60	7.684%	$172.9405	$172.94	$172.95	$172.90
Purchase #2	$141.38	10.537%	$156.2772	$156.28	$156.30	$156.30
Purchase #3	$45.38	12.729%	$51.1564	$51.16	$51.15	$51.20
Purchase #4	$29.28	4.272%	$30.5308	$30.53	$30.55	$30.50
Purchase #5	$210.32	11.855%	$235.2534	$235.25	$235.25	$235.30
Purchase #6	$152.81	11.834%	$170.8935	$170.89	$170.90	$170.90
Purchase #7	$49.70	9.829%	$54.585	$54.59	$54.60	$54.60
7 purchase totals =	$789.47		$871.6368	$871.64	$871.70	$871.70