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	$246.83	5.606%	$260.6673	$260.67	$260.65	$260.70
Purchase #2	$145.60	3.786%	$151.1124	$151.11	$151.10	$151.10
Purchase #3	$96.51	7.333%	$103.5871	$103.59	$103.60	$103.60
Purchase #4	$43.83	13.826%	$49.8899	$49.89	$49.90	$49.90
Purchase #5	$188.60	6.357%	$200.5893	$200.59	$200.60	$200.60
Purchase #6	$166.28	13.774%	$189.1834	$189.18	$189.20	$189.20
Purchase #7	$64.88	10.762%	$71.8624	$71.86	$71.85	$71.90
7 purchase totals =	$952.53		$1,026.8918	$1,026.89	$1,026.90	$1,027.00