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	$47.26	11.503%	$52.6963	$52.70	$52.70	$52.70
Purchase #2	$95.61	5.416%	$100.7882	$100.79	$100.80	$100.80
Purchase #3	$106.39	9.825%	$116.8428	$116.84	$116.85	$116.80
Purchase #4	$57.85	4.587%	$60.5036	$60.50	$60.50	$60.50
Purchase #5	$171.62	12.516%	$193.1	$193.10	$193.10	$193.10
Purchase #6	$97.51	8.178%	$105.4844	$105.48	$105.50	$105.50
Purchase #7	$197.57	12.818%	$222.8945	$222.89	$222.90	$222.90
7 purchase totals =	$773.81		$852.3098	$852.30	$852.35	$852.30