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	$59.38	4.746%	$62.1982	$62.20	$62.20	$62.20
Purchase #2	$235.45	11.583%	$262.7222	$262.72	$262.70	$262.70
Purchase #3	$92.55	11.111%	$102.8332	$102.83	$102.85	$102.80
Purchase #4	$54.74	8.594%	$59.4444	$59.44	$59.45	$59.40
Purchase #5	$215.50	5.661%	$227.6995	$227.70	$227.70	$227.70
Purchase #6	$130.80	10.361%	$144.3522	$144.35	$144.35	$144.40
Purchase #7	$225.89	10.503%	$249.6152	$249.62	$249.60	$249.60
7 purchase totals =	$1,014.31		$1,108.8649	$1,108.86	$1,108.85	$1,108.80