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	$201.56	13.156%	$228.0772	$228.08	$228.10	$228.10
Purchase #2	$17.38	7.491%	$18.6819	$18.68	$18.70	$18.70
Purchase #3	$81.46	10.683%	$90.1624	$90.16	$90.15	$90.20
Purchase #4	$157.42	3.510%	$162.9454	$162.95	$162.95	$162.90
Purchase #5	$248.31	12.524%	$279.4083	$279.41	$279.40	$279.40
Purchase #6	$7.89	5.813%	$8.3486	$8.35	$8.35	$8.30
Purchase #7	$228.29	11.173%	$253.7968	$253.80	$253.80	$253.80
7 purchase totals =	$942.31		$1,041.4206	$1,041.43	$1,041.45	$1,041.40