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	$14.86	11.216%	$16.5267	$16.53	$16.55	$16.50
Purchase #2	$73.28	10.501%	$80.9751	$80.98	$81.00	$81.00
Purchase #3	$82.37	3.653%	$85.379	$85.38	$85.40	$85.40
Purchase #4	$144.85	12.249%	$162.5927	$162.59	$162.60	$162.60
Purchase #5	$249.25	11.650%	$278.2876	$278.29	$278.30	$278.30
Purchase #6	$156.89	7.506%	$168.6662	$168.67	$168.65	$168.70
Purchase #7	$116.89	9.278%	$127.7351	$127.74	$127.75	$127.70
7 purchase totals =	$838.39		$920.1624	$920.18	$920.25	$920.20