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	$66.76	13.861%	$76.0136	$76.01	$76.00	$76.00
Purchase #2	$166.35	12.726%	$187.5197	$187.52	$187.50	$187.50
Purchase #3	$156.47	7.511%	$168.2225	$168.22	$168.20	$168.20
Purchase #4	$67.93	5.406%	$71.6023	$71.60	$71.60	$71.60
Purchase #5	$179.89	8.318%	$194.8533	$194.85	$194.85	$194.90
Purchase #6	$65.25	13.132%	$73.8186	$73.82	$73.80	$73.80
Purchase #7	$160.38	4.854%	$168.1648	$168.16	$168.15	$168.20
7 purchase totals =	$863.03		$940.1948	$940.18	$940.10	$940.20