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	$217.62	4.585%	$227.5979	$227.60	$227.60	$227.60
Purchase #2	$62.67	7.852%	$67.5908	$67.59	$67.60	$67.60
Purchase #3	$171.47	13.588%	$194.7693	$194.77	$194.75	$194.80
Purchase #4	$72.54	10.139%	$79.8948	$79.89	$79.90	$79.90
Purchase #5	$46.40	8.834%	$50.499	$50.50	$50.50	$50.50
Purchase #6	$168.69	9.339%	$184.444	$184.44	$184.45	$184.40
Purchase #7	$199.86	11.690%	$223.2236	$223.22	$223.20	$223.20
7 purchase totals =	$939.25		$1,028.0194	$1,028.01	$1,028.00	$1,028.00