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	$135.72	9.247%	$148.27	$148.27	$148.25	$148.30
Purchase #2	$75.77	10.183%	$83.4857	$83.49	$83.50	$83.50
Purchase #3	$120.25	9.824%	$132.0634	$132.06	$132.05	$132.10
Purchase #4	$127.86	9.285%	$139.7318	$139.73	$139.75	$139.70
Purchase #5	$54.50	4.556%	$56.983	$56.98	$57.00	$57.00
Purchase #6	$44.34	10.698%	$49.0835	$49.08	$49.10	$49.10
Purchase #7	$152.88	3.689%	$158.5197	$158.52	$158.50	$158.50
7 purchase totals =	$711.32		$768.1371	$768.13	$768.15	$768.20