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	$21.82	13.642%	$24.7967	$24.80	$24.80	$24.80
Purchase #2	$13.30	4.506%	$13.8993	$13.90	$13.90	$13.90
Purchase #3	$92.92	13.463%	$105.4298	$105.43	$105.45	$105.40
Purchase #4	$30.81	8.460%	$33.4165	$33.42	$33.40	$33.40
Purchase #5	$154.87	6.474%	$164.8963	$164.90	$164.90	$164.90
Purchase #6	$198.83	12.131%	$222.9501	$222.95	$222.95	$223.00
Purchase #7	$53.60	11.703%	$59.8728	$59.87	$59.85	$59.90
7 purchase totals =	$566.15		$625.2615	$625.27	$625.25	$625.30