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	$18.54	4.704%	$19.4121	$19.41	$19.40	$19.40
Purchase #2	$235.93	4.389%	$246.285	$246.29	$246.30	$246.30
Purchase #3	$18.64	8.731%	$20.2675	$20.27	$20.25	$20.30
Purchase #4	$206.91	7.577%	$222.5876	$222.59	$222.60	$222.60
Purchase #5	$57.59	13.262%	$65.2276	$65.23	$65.25	$65.20
Purchase #6	$100.28	13.158%	$113.4748	$113.47	$113.45	$113.50
Purchase #7	$233.94	13.133%	$264.6633	$264.66	$264.65	$264.70
7 purchase totals =	$871.83		$951.9179	$951.92	$951.90	$952.00