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	$245.28	7.644%	$264.0292	$264.03	$264.05	$264.00
Purchase #2	$30.76	12.800%	$34.6973	$34.70	$34.70	$34.70
Purchase #3	$121.28	4.265%	$126.4526	$126.45	$126.45	$126.50
Purchase #4	$181.89	8.136%	$196.6886	$196.69	$196.70	$196.70
Purchase #5	$152.56	11.815%	$170.585	$170.59	$170.60	$170.60
Purchase #6	$51.32	10.795%	$56.86	$56.86	$56.85	$56.90
Purchase #7	$46.54	3.188%	$48.0237	$48.02	$48.00	$48.00
7 purchase totals =	$829.63		$897.3364	$897.34	$897.35	$897.40