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	$88.81	3.403%	$91.8322	$91.83	$91.85	$91.80
Purchase #2	$64.68	12.734%	$72.9164	$72.92	$72.90	$72.90
Purchase #3	$43.98	12.782%	$49.6015	$49.60	$49.60	$49.60
Purchase #4	$228.40	10.313%	$251.9549	$251.95	$251.95	$252.00
Purchase #5	$232.87	7.166%	$249.5575	$249.56	$249.55	$249.60
Purchase #6	$150.87	11.519%	$168.2487	$168.25	$168.25	$168.20
Purchase #7	$154.85	11.174%	$172.1529	$172.15	$172.15	$172.20
7 purchase totals =	$964.46		$1,056.2641	$1,056.26	$1,056.25	$1,056.30