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	$228.35	13.641%	$259.4992	$259.50	$259.50	$259.50
Purchase #2	$211.33	3.435%	$218.5892	$218.59	$218.60	$218.60
Purchase #3	$237.58	9.180%	$259.3898	$259.39	$259.40	$259.40
Purchase #4	$171.71	5.116%	$180.4947	$180.49	$180.50	$180.50
Purchase #5	$99.92	11.308%	$111.219	$111.22	$111.20	$111.20
Purchase #6	$211.39	3.328%	$218.4251	$218.43	$218.45	$218.40
Purchase #7	$93.47	8.211%	$101.1448	$101.14	$101.15	$101.10
7 purchase totals =	$1,253.75		$1,348.7618	$1,348.76	$1,348.80	$1,348.70