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	$211.46	3.768%	$219.4278	$219.43	$219.45	$219.40
Purchase #2	$118.78	3.640%	$123.1036	$123.10	$123.10	$123.10
Purchase #3	$55.62	13.589%	$63.1782	$63.18	$63.20	$63.20
Purchase #4	$211.57	9.132%	$230.8906	$230.89	$230.90	$230.90
Purchase #5	$19.30	8.191%	$20.8809	$20.88	$20.90	$20.90
Purchase #6	$132.46	5.615%	$139.8976	$139.90	$139.90	$139.90
Purchase #7	$91.99	8.280%	$99.6068	$99.61	$99.60	$99.60
7 purchase totals =	$841.18		$896.9855	$896.99	$897.05	$897.00