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	$38.87	12.120%	$43.581	$43.58	$43.60	$43.60
Purchase #2	$18.87	7.419%	$20.27	$20.27	$20.25	$20.30
Purchase #3	$24.86	6.667%	$26.5174	$26.52	$26.50	$26.50
Purchase #4	$63.70	4.824%	$66.7729	$66.77	$66.75	$66.80
Purchase #5	$13.96	5.870%	$14.7795	$14.78	$14.80	$14.80
Purchase #6	$222.91	7.738%	$240.1588	$240.16	$240.15	$240.20
Purchase #7	$83.32	8.793%	$90.6463	$90.65	$90.65	$90.60
7 purchase totals =	$466.49		$502.7259	$502.73	$502.70	$502.80