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	$244.39	11.137%	$271.6077	$271.61	$271.60	$271.60
Purchase #2	$119.40	3.738%	$123.8632	$123.86	$123.85	$123.90
Purchase #3	$221.34	12.635%	$249.3063	$249.31	$249.30	$249.30
Purchase #4	$83.63	13.363%	$94.8055	$94.81	$94.80	$94.80
Purchase #5	$31.69	3.595%	$32.8293	$32.83	$32.85	$32.80
Purchase #6	$173.95	6.129%	$184.6114	$184.61	$184.60	$184.60
Purchase #7	$100.93	10.254%	$111.2794	$111.28	$111.30	$111.30
7 purchase totals =	$975.33		$1,068.3028	$1,068.31	$1,068.30	$1,068.30