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	$196.88	11.834%	$220.1788	$220.18	$220.20	$220.20
Purchase #2	$247.35	7.758%	$266.5394	$266.54	$266.55	$266.50
Purchase #3	$32.71	13.810%	$37.2273	$37.23	$37.25	$37.20
Purchase #4	$65.47	4.286%	$68.276	$68.28	$68.30	$68.30
Purchase #5	$204.28	8.833%	$222.3241	$222.32	$222.30	$222.30
Purchase #6	$68.64	5.500%	$72.4152	$72.42	$72.40	$72.40
Purchase #7	$194.95	13.793%	$221.8395	$221.84	$221.85	$221.80
7 purchase totals =	$1,010.28		$1,108.8003	$1,108.81	$1,108.85	$1,108.70