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	$116.34	11.229%	$129.4038	$129.40	$129.40	$129.40
Purchase #2	$105.72	5.667%	$111.7112	$111.71	$111.70	$111.70
Purchase #3	$41.49	6.872%	$44.3412	$44.34	$44.35	$44.30
Purchase #4	$126.32	13.285%	$143.1016	$143.10	$143.10	$143.10
Purchase #5	$139.96	9.738%	$153.5893	$153.59	$153.60	$153.60
Purchase #6	$11.39	8.614%	$12.3711	$12.37	$12.35	$12.40
Purchase #7	$124.52	11.410%	$138.7277	$138.73	$138.75	$138.70
7 purchase totals =	$665.74		$733.2459	$733.24	$733.25	$733.20