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	$89.94	6.701%	$95.9669	$95.97	$95.95	$96.00
Purchase #2	$224.71	9.860%	$246.8664	$246.87	$246.85	$246.90
Purchase #3	$116.48	6.158%	$123.6528	$123.65	$123.65	$123.70
Purchase #4	$52.91	8.561%	$57.4396	$57.44	$57.45	$57.40
Purchase #5	$210.89	4.136%	$219.6124	$219.61	$219.60	$219.60
Purchase #6	$33.83	13.591%	$38.4278	$38.43	$38.45	$38.40
Purchase #7	$47.64	10.425%	$52.6065	$52.61	$52.60	$52.60
7 purchase totals =	$776.40		$834.5724	$834.58	$834.55	$834.60