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	$52.56	13.419%	$59.613	$59.61	$59.60	$59.60
Purchase #2	$219.49	8.713%	$238.6142	$238.61	$238.60	$238.60
Purchase #3	$198.68	12.717%	$223.9461	$223.95	$223.95	$223.90
Purchase #4	$236.50	5.496%	$249.498	$249.50	$249.50	$249.50
Purchase #5	$224.51	11.713%	$250.8069	$250.81	$250.80	$250.80
Purchase #6	$186.98	6.624%	$199.3656	$199.37	$199.35	$199.40
Purchase #7	$176.94	7.499%	$190.2087	$190.21	$190.20	$190.20
7 purchase totals =	$1,295.66		$1,412.0525	$1,412.06	$1,412.00	$1,412.00