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	$193.47	7.515%	$208.0093	$208.01	$208.00	$208.00
Purchase #2	$11.76	6.148%	$12.483	$12.48	$12.50	$12.50
Purchase #3	$17.92	3.770%	$18.5956	$18.60	$18.60	$18.60
Purchase #4	$28.56	10.852%	$31.6593	$31.66	$31.65	$31.70
Purchase #5	$98.76	13.335%	$111.9296	$111.93	$111.95	$111.90
Purchase #6	$137.28	11.760%	$153.4241	$153.42	$153.40	$153.40
Purchase #7	$103.65	13.221%	$117.3536	$117.35	$117.35	$117.40
7 purchase totals =	$591.40		$653.4545	$653.45	$653.45	$653.50