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	$109.90	12.570%	$123.7144	$123.71	$123.70	$123.70
Purchase #2	$209.41	5.663%	$221.2689	$221.27	$221.25	$221.30
Purchase #3	$124.32	6.874%	$132.8658	$132.87	$132.85	$132.90
Purchase #4	$217.48	9.509%	$238.1602	$238.16	$238.15	$238.20
Purchase #5	$54.51	12.411%	$61.2752	$61.28	$61.30	$61.30
Purchase #6	$197.58	7.243%	$211.8907	$211.89	$211.90	$211.90
Purchase #7	$99.98	13.208%	$113.1854	$113.19	$113.20	$113.20
7 purchase totals =	$1,013.18		$1,102.3606	$1,102.37	$1,102.35	$1,102.50