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	$60.90	7.697%	$65.5875	$65.59	$65.60	$65.60
Purchase #2	$111.80	4.290%	$116.5962	$116.60	$116.60	$116.60
Purchase #3	$73.43	3.604%	$76.0764	$76.08	$76.10	$76.10
Purchase #4	$51.92	13.355%	$58.8539	$58.85	$58.85	$58.90
Purchase #5	$161.87	7.196%	$173.5182	$173.52	$173.50	$173.50
Purchase #6	$119.34	3.789%	$123.8618	$123.86	$123.85	$123.90
Purchase #7	$32.63	11.814%	$36.4849	$36.48	$36.50	$36.50
7 purchase totals =	$611.89		$650.9789	$650.98	$651.00	$651.10