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	$30.53	6.628%	$32.5535	$32.55	$32.55	$32.60
Purchase #2	$31.68	5.602%	$33.4547	$33.45	$33.45	$33.50
Purchase #3	$33.89	9.247%	$37.0238	$37.02	$37.00	$37.00
Purchase #4	$173.99	9.500%	$190.5191	$190.52	$190.50	$190.50
Purchase #5	$21.48	5.310%	$22.6206	$22.62	$22.60	$22.60
Purchase #6	$76.86	12.304%	$86.3169	$86.32	$86.30	$86.30
Purchase #7	$208.68	7.637%	$224.6169	$224.62	$224.60	$224.60
7 purchase totals =	$577.11		$627.1055	$627.10	$627.00	$627.10