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	$40.27	11.111%	$44.7444	$44.74	$44.75	$44.70
Purchase #2	$73.38	6.399%	$78.0756	$78.08	$78.10	$78.10
Purchase #3	$98.81	13.302%	$111.9537	$111.95	$111.95	$112.00
Purchase #4	$85.78	5.706%	$90.6746	$90.67	$90.65	$90.70
Purchase #5	$196.62	11.678%	$219.5813	$219.58	$219.60	$219.60
Purchase #6	$204.57	6.660%	$218.1944	$218.19	$218.20	$218.20
Purchase #7	$197.81	9.621%	$216.8413	$216.84	$216.85	$216.80
7 purchase totals =	$897.24		$980.0653	$980.05	$980.10	$980.10