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	$33.32	9.805%	$36.587	$36.59	$36.60	$36.60
Purchase #2	$200.80	10.293%	$221.4683	$221.47	$221.45	$221.50
Purchase #3	$151.78	3.802%	$157.5507	$157.55	$157.55	$157.60
Purchase #4	$59.58	8.221%	$64.4781	$64.48	$64.50	$64.50
Purchase #5	$14.35	6.149%	$15.2324	$15.23	$15.25	$15.20
Purchase #6	$33.73	10.811%	$37.3766	$37.38	$37.40	$37.40
Purchase #7	$180.66	10.359%	$199.3746	$199.37	$199.35	$199.40
7 purchase totals =	$674.22		$732.0677	$732.07	$732.10	$732.20