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	$64.86	5.148%	$68.199	$68.20	$68.20	$68.20
Purchase #2	$19.59	8.661%	$21.2867	$21.29	$21.30	$21.30
Purchase #3	$68.27	3.744%	$70.826	$70.83	$70.85	$70.80
Purchase #4	$190.59	11.544%	$212.5917	$212.59	$212.60	$212.60
Purchase #5	$38.72	7.543%	$41.6406	$41.64	$41.65	$41.60
Purchase #6	$208.79	6.547%	$222.4595	$222.46	$222.45	$222.50
Purchase #7	$214.95	7.598%	$231.2819	$231.28	$231.30	$231.30
7 purchase totals =	$805.77		$868.2854	$868.29	$868.35	$868.30