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	$206.98	4.776%	$216.8654	$216.87	$216.85	$216.90
Purchase #2	$162.34	4.130%	$169.0446	$169.04	$169.05	$169.00
Purchase #3	$234.89	5.631%	$248.1167	$248.12	$248.10	$248.10
Purchase #4	$98.75	7.119%	$105.78	$105.78	$105.80	$105.80
Purchase #5	$58.43	13.844%	$66.519	$66.52	$66.50	$66.50
Purchase #6	$72.96	8.198%	$78.9413	$78.94	$78.95	$78.90
Purchase #7	$72.27	7.133%	$77.425	$77.43	$77.45	$77.40
7 purchase totals =	$906.62		$962.6920	$962.70	$962.70	$962.60