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	$200.67	4.442%	$209.5838	$209.58	$209.60	$209.60
Purchase #2	$36.41	5.462%	$38.3987	$38.40	$38.40	$38.40
Purchase #3	$72.33	12.292%	$81.2208	$81.22	$81.20	$81.20
Purchase #4	$146.82	12.808%	$165.6247	$165.62	$165.60	$165.60
Purchase #5	$117.32	7.852%	$126.532	$126.53	$126.55	$126.50
Purchase #6	$235.32	8.552%	$255.4446	$255.44	$255.45	$255.40
Purchase #7	$158.38	11.631%	$176.8012	$176.80	$176.80	$176.80
7 purchase totals =	$967.25		$1,053.6058	$1,053.59	$1,053.60	$1,053.50