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	$67.27	6.467%	$71.6204	$71.62	$71.60	$71.60
Purchase #2	$241.70	4.219%	$251.8973	$251.90	$251.90	$251.90
Purchase #3	$24.76	12.524%	$27.8609	$27.86	$27.85	$27.90
Purchase #4	$77.39	4.786%	$81.0939	$81.09	$81.10	$81.10
Purchase #5	$202.89	9.482%	$222.128	$222.13	$222.15	$222.10
Purchase #6	$145.43	4.363%	$151.7751	$151.78	$151.80	$151.80
Purchase #7	$153.32	5.777%	$162.1773	$162.18	$162.20	$162.20
7 purchase totals =	$912.76		$968.5529	$968.56	$968.60	$968.60