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	$21.57	5.260%	$22.7046	$22.70	$22.70	$22.70
Purchase #2	$18.92	13.207%	$21.4188	$21.42	$21.40	$21.40
Purchase #3	$50.76	4.210%	$52.897	$52.90	$52.90	$52.90
Purchase #4	$176.64	6.695%	$188.466	$188.47	$188.45	$188.50
Purchase #5	$241.60	11.345%	$269.0095	$269.01	$269.00	$269.00
Purchase #6	$125.71	10.688%	$139.1459	$139.15	$139.15	$139.10
Purchase #7	$11.37	13.539%	$12.9094	$12.91	$12.90	$12.90
7 purchase totals =	$646.57		$706.5512	$706.56	$706.50	$706.50