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	$66.95	4.206%	$69.7659	$69.77	$69.75	$69.80
Purchase #2	$47.80	9.579%	$52.3788	$52.38	$52.40	$52.40
Purchase #3	$238.43	11.276%	$265.3154	$265.32	$265.30	$265.30
Purchase #4	$24.45	5.588%	$25.8163	$25.82	$25.80	$25.80
Purchase #5	$103.36	5.353%	$108.8929	$108.89	$108.90	$108.90
Purchase #6	$116.94	5.284%	$123.1191	$123.12	$123.10	$123.10
Purchase #7	$99.92	11.512%	$111.4228	$111.42	$111.40	$111.40
7 purchase totals =	$697.85		$756.7112	$756.72	$756.65	$756.70