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	$77.93	11.176%	$86.6395	$86.64	$86.65	$86.60
Purchase #2	$85.55	5.673%	$90.4033	$90.40	$90.40	$90.40
Purchase #3	$237.70	10.476%	$262.6015	$262.60	$262.60	$262.60
Purchase #4	$161.57	11.795%	$180.6272	$180.63	$180.65	$180.60
Purchase #5	$181.94	5.870%	$192.6199	$192.62	$192.60	$192.60
Purchase #6	$10.66	11.512%	$11.8872	$11.89	$11.90	$11.90
Purchase #7	$87.70	4.332%	$91.4992	$91.50	$91.50	$91.50
7 purchase totals =	$843.05		$916.2778	$916.28	$916.30	$916.20