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	$207.54	8.805%	$225.8139	$225.81	$225.80	$225.80
Purchase #2	$214.47	11.350%	$238.8123	$238.81	$238.80	$238.80
Purchase #3	$192.40	13.312%	$218.0123	$218.01	$218.00	$218.00
Purchase #4	$117.96	4.650%	$123.4451	$123.45	$123.45	$123.40
Purchase #5	$96.66	13.320%	$109.5351	$109.54	$109.55	$109.50
Purchase #6	$33.80	11.217%	$37.5913	$37.59	$37.60	$37.60
Purchase #7	$142.74	6.281%	$151.7055	$151.71	$151.70	$151.70
7 purchase totals =	$1,005.57		$1,104.9155	$1,104.92	$1,104.90	$1,104.80