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	$51.71	8.418%	$56.0629	$56.06	$56.05	$56.10
Purchase #2	$49.90	4.219%	$52.0053	$52.01	$52.00	$52.00
Purchase #3	$104.35	4.832%	$109.3922	$109.39	$109.40	$109.40
Purchase #4	$195.34	10.725%	$216.2902	$216.29	$216.30	$216.30
Purchase #5	$26.64	6.531%	$28.3799	$28.38	$28.40	$28.40
Purchase #6	$186.54	13.613%	$211.9337	$211.93	$211.95	$211.90
Purchase #7	$61.41	4.390%	$64.1059	$64.11	$64.10	$64.10
7 purchase totals =	$675.89		$738.1701	$738.17	$738.20	$738.20