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	$98.43	4.307%	$102.6694	$102.67	$102.65	$102.70
Purchase #2	$54.40	3.784%	$56.4585	$56.46	$56.45	$56.50
Purchase #3	$16.66	10.855%	$18.4684	$18.47	$18.45	$18.50
Purchase #4	$244.56	4.635%	$255.8954	$255.90	$255.90	$255.90
Purchase #5	$145.73	3.264%	$150.4866	$150.49	$150.50	$150.50
Purchase #6	$62.37	8.719%	$67.808	$67.81	$67.80	$67.80
Purchase #7	$65.72	6.701%	$70.1239	$70.12	$70.10	$70.10
7 purchase totals =	$687.87		$721.9102	$721.92	$721.85	$722.00