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	$48.38	11.501%	$53.9442	$53.94	$53.95	$53.90
Purchase #2	$151.96	5.279%	$159.982	$159.98	$160.00	$160.00
Purchase #3	$138.47	3.700%	$143.5934	$143.59	$143.60	$143.60
Purchase #4	$77.35	10.368%	$85.3696	$85.37	$85.35	$85.40
Purchase #5	$101.65	4.135%	$105.8532	$105.85	$105.85	$105.90
Purchase #6	$19.32	4.680%	$20.2242	$20.22	$20.20	$20.20
Purchase #7	$45.34	7.556%	$48.7659	$48.77	$48.75	$48.80
7 purchase totals =	$582.47		$617.7325	$617.72	$617.70	$617.80