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	$99.30	8.372%	$107.6134	$107.61	$107.60	$107.60
Purchase #2	$234.95	5.378%	$247.5856	$247.59	$247.60	$247.60
Purchase #3	$129.29	4.713%	$135.3834	$135.38	$135.40	$135.40
Purchase #4	$65.27	11.758%	$72.9444	$72.94	$72.95	$72.90
Purchase #5	$167.52	9.473%	$183.3892	$183.39	$183.40	$183.40
Purchase #6	$105.32	3.548%	$109.0568	$109.06	$109.05	$109.10
Purchase #7	$181.25	4.860%	$190.0588	$190.06	$190.05	$190.10
7 purchase totals =	$982.90		$1,046.0316	$1,046.03	$1,046.05	$1,046.10