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	$101.73	3.381%	$105.1695	$105.17	$105.15	$105.20
Purchase #2	$248.28	5.485%	$261.8982	$261.90	$261.90	$261.90
Purchase #3	$87.76	13.732%	$99.8112	$99.81	$99.80	$99.80
Purchase #4	$41.82	9.634%	$45.8489	$45.85	$45.85	$45.80
Purchase #5	$62.52	12.664%	$70.4375	$70.44	$70.45	$70.40
Purchase #6	$162.97	10.295%	$179.7478	$179.75	$179.75	$179.70
Purchase #7	$39.72	6.730%	$42.3932	$42.39	$42.40	$42.40
7 purchase totals =	$744.80		$805.3063	$805.31	$805.30	$805.20