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	$240.87	7.555%	$259.0677	$259.07	$259.05	$259.10
Purchase #2	$54.96	10.172%	$60.5505	$60.55	$60.55	$60.60
Purchase #3	$72.79	11.205%	$80.9461	$80.95	$80.95	$80.90
Purchase #4	$66.44	7.786%	$71.613	$71.61	$71.60	$71.60
Purchase #5	$42.94	12.292%	$48.2182	$48.22	$48.20	$48.20
Purchase #6	$162.46	6.136%	$172.4285	$172.43	$172.45	$172.40
Purchase #7	$57.46	7.849%	$61.97	$61.97	$61.95	$62.00
7 purchase totals =	$697.92		$754.7940	$754.80	$754.75	$754.80