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	$201.92	13.755%	$229.6941	$229.69	$229.70	$229.70
Purchase #2	$134.54	11.431%	$149.9193	$149.92	$149.90	$149.90
Purchase #3	$115.59	10.159%	$127.3328	$127.33	$127.35	$127.30
Purchase #4	$66.64	8.289%	$72.1638	$72.16	$72.15	$72.20
Purchase #5	$152.97	13.377%	$173.4328	$173.43	$173.45	$173.40
Purchase #6	$134.78	12.180%	$151.1962	$151.20	$151.20	$151.20
Purchase #7	$222.48	3.311%	$229.8463	$229.85	$229.85	$229.80
7 purchase totals =	$1,028.92		$1,133.5853	$1,133.58	$1,133.60	$1,133.50