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	$158.69	10.836%	$175.8856	$175.89	$175.90	$175.90
Purchase #2	$90.61	10.205%	$99.8568	$99.86	$99.85	$99.90
Purchase #3	$108.68	3.642%	$112.6381	$112.64	$112.65	$112.60
Purchase #4	$173.61	11.861%	$194.2019	$194.20	$194.20	$194.20
Purchase #5	$58.81	4.113%	$61.2289	$61.23	$61.25	$61.20
Purchase #6	$60.85	8.403%	$65.9632	$65.96	$65.95	$66.00
Purchase #7	$200.35	8.490%	$217.3597	$217.36	$217.35	$217.40
7 purchase totals =	$851.60		$927.1342	$927.14	$927.15	$927.20