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	$244.95	8.702%	$266.2655	$266.27	$266.25	$266.30
Purchase #2	$18.39	13.529%	$20.878	$20.88	$20.90	$20.90
Purchase #3	$113.89	4.490%	$119.0037	$119.00	$119.00	$119.00
Purchase #4	$15.76	8.857%	$17.1559	$17.16	$17.15	$17.20
Purchase #5	$34.56	9.167%	$37.7281	$37.73	$37.75	$37.70
Purchase #6	$136.55	7.350%	$146.5864	$146.59	$146.60	$146.60
Purchase #7	$96.46	4.478%	$100.7795	$100.78	$100.80	$100.80
7 purchase totals =	$660.56		$708.3971	$708.41	$708.45	$708.50