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	$65.40	10.607%	$72.337	$72.34	$72.35	$72.30
Purchase #2	$31.33	8.571%	$34.0153	$34.02	$34.00	$34.00
Purchase #3	$48.77	8.454%	$52.893	$52.89	$52.90	$52.90
Purchase #4	$32.51	6.423%	$34.5981	$34.60	$34.60	$34.60
Purchase #5	$108.54	4.804%	$113.7543	$113.75	$113.75	$113.80
Purchase #6	$25.42	11.777%	$28.4137	$28.41	$28.40	$28.40
Purchase #7	$99.62	3.867%	$103.4723	$103.47	$103.45	$103.50
7 purchase totals =	$411.59		$439.4837	$439.48	$439.45	$439.50