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	$216.86	11.144%	$241.0269	$241.03	$241.05	$241.00
Purchase #2	$207.76	8.454%	$225.324	$225.32	$225.30	$225.30
Purchase #3	$211.25	3.764%	$219.2015	$219.20	$219.20	$219.20
Purchase #4	$133.77	4.526%	$139.8244	$139.82	$139.80	$139.80
Purchase #5	$222.81	4.176%	$232.1145	$232.11	$232.10	$232.10
Purchase #6	$238.91	6.573%	$254.6136	$254.61	$254.60	$254.60
Purchase #7	$83.88	6.643%	$89.4521	$89.45	$89.45	$89.50
7 purchase totals =	$1,315.24		$1,401.5570	$1,401.54	$1,401.50	$1,401.50