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	$206.61	5.846%	$218.6884	$218.69	$218.70	$218.70
Purchase #2	$31.92	4.794%	$33.4502	$33.45	$33.45	$33.50
Purchase #3	$202.60	10.725%	$224.3289	$224.33	$224.35	$224.30
Purchase #4	$50.75	8.186%	$54.9044	$54.90	$54.90	$54.90
Purchase #5	$178.74	7.630%	$192.3779	$192.38	$192.40	$192.40
Purchase #6	$99.39	12.293%	$111.608	$111.61	$111.60	$111.60
Purchase #7	$187.38	13.562%	$212.7925	$212.79	$212.80	$212.80
7 purchase totals =	$957.39		$1,048.1503	$1,048.15	$1,048.20	$1,048.20