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	$218.76	7.643%	$235.4798	$235.48	$235.50	$235.50
Purchase #2	$115.52	3.433%	$119.4858	$119.49	$119.50	$119.50
Purchase #3	$113.75	13.212%	$128.7787	$128.78	$128.80	$128.80
Purchase #4	$42.41	4.664%	$44.388	$44.39	$44.40	$44.40
Purchase #5	$225.95	5.621%	$238.6506	$238.65	$238.65	$238.70
Purchase #6	$77.27	10.770%	$85.592	$85.59	$85.60	$85.60
Purchase #7	$147.88	13.265%	$167.4963	$167.50	$167.50	$167.50
7 purchase totals =	$941.54		$1,019.8712	$1,019.88	$1,019.95	$1,020.00