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	$143.99	7.822%	$155.2529	$155.25	$155.25	$155.30
Purchase #2	$29.77	7.163%	$31.9024	$31.90	$31.90	$31.90
Purchase #3	$99.67	11.796%	$111.4271	$111.43	$111.45	$111.40
Purchase #4	$68.64	13.489%	$77.8988	$77.90	$77.90	$77.90
Purchase #5	$108.38	4.833%	$113.618	$113.62	$113.60	$113.60
Purchase #6	$25.41	8.565%	$27.5864	$27.59	$27.60	$27.60
Purchase #7	$25.98	6.142%	$27.5757	$27.58	$27.60	$27.60
7 purchase totals =	$501.84		$545.2613	$545.27	$545.30	$545.30