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	$238.57	10.420%	$263.429	$263.43	$263.45	$263.40
Purchase #2	$8.51	11.851%	$9.5185	$9.52	$9.50	$9.50
Purchase #3	$78.59	5.656%	$83.0351	$83.04	$83.05	$83.00
Purchase #4	$60.41	7.838%	$65.1449	$65.14	$65.15	$65.10
Purchase #5	$12.83	11.174%	$14.2636	$14.26	$14.25	$14.30
Purchase #6	$150.52	10.720%	$166.6557	$166.66	$166.65	$166.70
Purchase #7	$123.49	6.310%	$131.2822	$131.28	$131.30	$131.30
7 purchase totals =	$672.92		$733.3290	$733.33	$733.35	$733.30