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	$46.66	4.849%	$48.9225	$48.92	$48.90	$48.90
Purchase #2	$54.77	10.629%	$60.5915	$60.59	$60.60	$60.60
Purchase #3	$168.68	10.873%	$187.0206	$187.02	$187.00	$187.00
Purchase #4	$166.72	11.789%	$186.3746	$186.37	$186.35	$186.40
Purchase #5	$243.79	6.601%	$259.8826	$259.88	$259.90	$259.90
Purchase #6	$145.72	5.615%	$153.9022	$153.90	$153.90	$153.90
Purchase #7	$203.37	4.839%	$213.2111	$213.21	$213.20	$213.20
7 purchase totals =	$1,029.71		$1,109.9051	$1,109.89	$1,109.85	$1,109.90