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	$92.47	10.231%	$101.9306	$101.93	$101.95	$101.90
Purchase #2	$223.72	6.336%	$237.8949	$237.89	$237.90	$237.90
Purchase #3	$102.95	6.429%	$109.5687	$109.57	$109.55	$109.60
Purchase #4	$56.95	10.222%	$62.7714	$62.77	$62.75	$62.80
Purchase #5	$34.48	5.475%	$36.3678	$36.37	$36.35	$36.40
Purchase #6	$96.79	11.103%	$107.5366	$107.54	$107.55	$107.50
Purchase #7	$59.45	12.391%	$66.8164	$66.82	$66.80	$66.80
7 purchase totals =	$666.81		$722.8864	$722.89	$722.85	$722.90