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	$134.52	5.413%	$141.8016	$141.80	$141.80	$141.80
Purchase #2	$142.46	4.131%	$148.345	$148.35	$148.35	$148.30
Purchase #3	$146.92	6.491%	$156.4566	$156.46	$156.45	$156.50
Purchase #4	$181.65	4.862%	$190.4818	$190.48	$190.50	$190.50
Purchase #5	$45.85	13.227%	$51.9146	$51.91	$51.90	$51.90
Purchase #6	$24.54	12.460%	$27.5977	$27.60	$27.60	$27.60
Purchase #7	$241.63	7.610%	$260.018	$260.02	$260.00	$260.00
7 purchase totals =	$917.57		$976.6153	$976.62	$976.60	$976.60