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	$136.52	7.626%	$146.931	$146.93	$146.95	$146.90
Purchase #2	$38.89	6.624%	$41.4661	$41.47	$41.45	$41.50
Purchase #3	$232.68	4.873%	$244.0185	$244.02	$244.00	$244.00
Purchase #4	$52.33	10.308%	$57.7242	$57.72	$57.70	$57.70
Purchase #5	$24.72	11.219%	$27.4933	$27.49	$27.50	$27.50
Purchase #6	$20.41	5.450%	$21.5223	$21.52	$21.50	$21.50
Purchase #7	$229.84	13.377%	$260.5857	$260.59	$260.60	$260.60
7 purchase totals =	$735.39		$799.7411	$799.74	$799.70	$799.70