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	$99.49	12.737%	$112.162	$112.16	$112.15	$112.20
Purchase #2	$58.35	3.858%	$60.6011	$60.60	$60.60	$60.60
Purchase #3	$197.58	12.821%	$222.9117	$222.91	$222.90	$222.90
Purchase #4	$155.82	5.463%	$164.3324	$164.33	$164.35	$164.30
Purchase #5	$159.90	7.820%	$172.4042	$172.40	$172.40	$172.40
Purchase #6	$72.28	12.157%	$81.0671	$81.07	$81.05	$81.10
Purchase #7	$169.69	8.660%	$184.3852	$184.39	$184.40	$184.40
7 purchase totals =	$913.11		$997.8637	$997.86	$997.85	$997.90