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	$94.45	11.693%	$105.494	$105.49	$105.50	$105.50
Purchase #2	$206.60	10.146%	$227.5616	$227.56	$227.55	$227.60
Purchase #3	$248.42	3.148%	$256.2403	$256.24	$256.25	$256.20
Purchase #4	$95.99	5.252%	$101.0314	$101.03	$101.05	$101.00
Purchase #5	$243.41	6.257%	$258.6402	$258.64	$258.65	$258.60
Purchase #6	$95.31	8.680%	$103.5829	$103.58	$103.60	$103.60
Purchase #7	$48.90	4.529%	$51.1147	$51.11	$51.10	$51.10
7 purchase totals =	$1,033.08		$1,103.6651	$1,103.65	$1,103.70	$1,103.60