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	$70.52	6.247%	$74.9254	$74.93	$74.95	$74.90
Purchase #2	$35.71	5.501%	$37.6744	$37.67	$37.65	$37.70
Purchase #3	$37.33	3.193%	$38.5219	$38.52	$38.50	$38.50
Purchase #4	$121.79	4.323%	$127.055	$127.06	$127.05	$127.10
Purchase #5	$155.80	13.787%	$177.2801	$177.28	$177.30	$177.30
Purchase #6	$125.93	12.852%	$142.1145	$142.11	$142.10	$142.10
Purchase #7	$14.42	10.464%	$15.9289	$15.93	$15.95	$15.90
7 purchase totals =	$561.50		$613.5002	$613.50	$613.50	$613.50