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	$212.39	6.860%	$226.96	$226.96	$226.95	$227.00
Purchase #2	$157.33	10.542%	$173.9157	$173.92	$173.90	$173.90
Purchase #3	$174.40	8.762%	$189.6809	$189.68	$189.70	$189.70
Purchase #4	$132.56	10.529%	$146.5172	$146.52	$146.50	$146.50
Purchase #5	$149.81	11.358%	$166.8254	$166.83	$166.85	$166.80
Purchase #6	$245.26	4.113%	$255.3475	$255.35	$255.35	$255.30
Purchase #7	$183.32	9.585%	$200.8912	$200.89	$200.90	$200.90
7 purchase totals =	$1,255.07		$1,360.1379	$1,360.15	$1,360.15	$1,360.10