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	$86.81	10.418%	$95.8539	$95.85	$95.85	$95.90
Purchase #2	$134.67	5.210%	$141.6863	$141.69	$141.70	$141.70
Purchase #3	$211.54	7.349%	$227.0861	$227.09	$227.10	$227.10
Purchase #4	$48.33	12.726%	$54.4805	$54.48	$54.50	$54.50
Purchase #5	$150.41	3.760%	$156.0654	$156.07	$156.05	$156.10
Purchase #6	$127.35	9.242%	$139.1197	$139.12	$139.10	$139.10
Purchase #7	$15.85	13.870%	$18.0484	$18.05	$18.05	$18.00
7 purchase totals =	$774.96		$832.3403	$832.35	$832.35	$832.40