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	$215.46	7.474%	$231.5635	$231.56	$231.55	$231.60
Purchase #2	$248.53	12.456%	$279.4869	$279.49	$279.50	$279.50
Purchase #3	$141.49	7.716%	$152.4074	$152.41	$152.40	$152.40
Purchase #4	$64.92	3.406%	$67.1312	$67.13	$67.15	$67.10
Purchase #5	$150.75	11.233%	$167.6837	$167.68	$167.70	$167.70
Purchase #6	$244.77	3.293%	$252.8303	$252.83	$252.85	$252.80
Purchase #7	$62.75	7.520%	$67.4688	$67.47	$67.45	$67.50
7 purchase totals =	$1,128.67		$1,218.5718	$1,218.57	$1,218.60	$1,218.60