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	$145.55	4.158%	$151.602	$151.60	$151.60	$151.60
Purchase #2	$30.35	11.102%	$33.7195	$33.72	$33.70	$33.70
Purchase #3	$134.88	13.675%	$153.3248	$153.32	$153.30	$153.30
Purchase #4	$11.29	4.772%	$11.8288	$11.83	$11.85	$11.80
Purchase #5	$120.66	9.488%	$132.1082	$132.11	$132.10	$132.10
Purchase #6	$56.68	7.409%	$60.8794	$60.88	$60.90	$60.90
Purchase #7	$151.32	11.202%	$168.2709	$168.27	$168.25	$168.30
7 purchase totals =	$650.73		$711.7336	$711.73	$711.70	$711.70