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	$137.66	5.201%	$144.8197	$144.82	$144.80	$144.80
Purchase #2	$55.52	8.772%	$60.3902	$60.39	$60.40	$60.40
Purchase #3	$213.84	5.364%	$225.3104	$225.31	$225.30	$225.30
Purchase #4	$203.40	4.479%	$212.5103	$212.51	$212.50	$212.50
Purchase #5	$48.91	11.731%	$54.6476	$54.65	$54.65	$54.60
Purchase #6	$29.65	5.400%	$31.2511	$31.25	$31.25	$31.30
Purchase #7	$14.52	6.576%	$15.4748	$15.47	$15.45	$15.50
7 purchase totals =	$703.50		$744.4041	$744.40	$744.35	$744.40