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	$209.92	13.186%	$237.6001	$237.60	$237.60	$237.60
Purchase #2	$232.76	9.773%	$255.5076	$255.51	$255.50	$255.50
Purchase #3	$185.42	12.494%	$208.5864	$208.59	$208.60	$208.60
Purchase #4	$56.94	6.333%	$60.546	$60.55	$60.55	$60.50
Purchase #5	$211.72	9.431%	$231.6873	$231.69	$231.70	$231.70
Purchase #6	$108.27	7.812%	$116.7281	$116.73	$116.75	$116.70
Purchase #7	$6.85	13.686%	$7.7875	$7.79	$7.80	$7.80
7 purchase totals =	$1,011.88		$1,118.4430	$1,118.46	$1,118.50	$1,118.40