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	$33.51	12.247%	$37.614	$37.61	$37.60	$37.60
Purchase #2	$30.76	5.676%	$32.5059	$32.51	$32.50	$32.50
Purchase #3	$85.54	3.613%	$88.6306	$88.63	$88.65	$88.60
Purchase #4	$17.93	10.766%	$19.8603	$19.86	$19.85	$19.90
Purchase #5	$136.61	13.723%	$155.357	$155.36	$155.35	$155.40
Purchase #6	$29.82	12.188%	$33.4545	$33.45	$33.45	$33.50
Purchase #7	$109.45	4.122%	$113.9615	$113.96	$113.95	$114.00
7 purchase totals =	$443.62		$481.3838	$481.38	$481.35	$481.50