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	$10.25	3.273%	$10.5855	$10.59	$10.60	$10.60
Purchase #2	$153.98	4.559%	$160.9999	$161.00	$161.00	$161.00
Purchase #3	$142.45	6.568%	$151.8061	$151.81	$151.80	$151.80
Purchase #4	$85.57	10.539%	$94.5882	$94.59	$94.60	$94.60
Purchase #5	$118.37	11.408%	$131.8736	$131.87	$131.85	$131.90
Purchase #6	$105.52	7.288%	$113.2103	$113.21	$113.20	$113.20
Purchase #7	$34.90	7.102%	$37.3786	$37.38	$37.40	$37.40
7 purchase totals =	$651.04		$700.4422	$700.45	$700.45	$700.50