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	$225.60	10.603%	$249.5204	$249.52	$249.50	$249.50
Purchase #2	$60.58	5.427%	$63.8677	$63.87	$63.85	$63.90
Purchase #3	$223.32	12.583%	$251.4204	$251.42	$251.40	$251.40
Purchase #4	$68.68	5.645%	$72.557	$72.56	$72.55	$72.60
Purchase #5	$105.88	3.378%	$109.4566	$109.46	$109.45	$109.50
Purchase #6	$158.58	7.120%	$169.8709	$169.87	$169.85	$169.90
Purchase #7	$204.46	10.414%	$225.7525	$225.75	$225.75	$225.80
7 purchase totals =	$1,047.10		$1,142.4455	$1,142.45	$1,142.35	$1,142.60