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	$199.30	8.120%	$215.4832	$215.48	$215.50	$215.50
Purchase #2	$200.49	13.526%	$227.6083	$227.61	$227.60	$227.60
Purchase #3	$182.42	8.113%	$197.2197	$197.22	$197.20	$197.20
Purchase #4	$226.39	3.543%	$234.411	$234.41	$234.40	$234.40
Purchase #5	$57.34	4.525%	$59.9346	$59.93	$59.95	$59.90
Purchase #6	$103.60	12.372%	$116.4174	$116.42	$116.40	$116.40
Purchase #7	$45.91	6.110%	$48.7151	$48.72	$48.70	$48.70
7 purchase totals =	$1,015.45		$1,099.7893	$1,099.79	$1,099.75	$1,099.70