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	$192.64	11.587%	$214.9612	$214.96	$214.95	$215.00
Purchase #2	$101.57	4.627%	$106.2696	$106.27	$106.25	$106.30
Purchase #3	$135.71	9.335%	$148.3785	$148.38	$148.40	$148.40
Purchase #4	$68.61	5.639%	$72.4789	$72.48	$72.50	$72.50
Purchase #5	$249.59	10.127%	$274.866	$274.87	$274.85	$274.90
Purchase #6	$132.66	6.592%	$141.4049	$141.40	$141.40	$141.40
Purchase #7	$119.27	6.607%	$127.1502	$127.15	$127.15	$127.20
7 purchase totals =	$1,000.05		$1,085.5093	$1,085.51	$1,085.50	$1,085.70