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	$246.55	6.554%	$262.7089	$262.71	$262.70	$262.70
Purchase #2	$168.35	9.598%	$184.5082	$184.51	$184.50	$184.50
Purchase #3	$35.53	4.617%	$37.1704	$37.17	$37.15	$37.20
Purchase #4	$83.45	8.238%	$90.3246	$90.32	$90.30	$90.30
Purchase #5	$34.71	10.682%	$38.4177	$38.42	$38.40	$38.40
Purchase #6	$16.80	12.478%	$18.8963	$18.90	$18.90	$18.90
Purchase #7	$99.65	4.585%	$104.219	$104.22	$104.20	$104.20
7 purchase totals =	$685.04		$736.2451	$736.25	$736.15	$736.20