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	$145.63	5.454%	$153.5727	$153.57	$153.55	$153.60
Purchase #2	$126.52	4.390%	$132.0742	$132.07	$132.05	$132.10
Purchase #3	$59.51	9.466%	$65.1432	$65.14	$65.15	$65.10
Purchase #4	$182.86	4.789%	$191.6172	$191.62	$191.60	$191.60
Purchase #5	$73.66	12.864%	$83.1356	$83.14	$83.15	$83.10
Purchase #6	$86.91	10.426%	$95.9712	$95.97	$95.95	$96.00
Purchase #7	$29.45	8.500%	$31.9533	$31.95	$31.95	$32.00
7 purchase totals =	$704.54		$753.4674	$753.46	$753.40	$753.50