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	$23.80	3.193%	$24.5599	$24.56	$24.55	$24.60
Purchase #2	$18.45	9.521%	$20.2066	$20.21	$20.20	$20.20
Purchase #3	$54.49	5.574%	$57.5273	$57.53	$57.55	$57.50
Purchase #4	$96.64	10.541%	$106.8268	$106.83	$106.85	$106.80
Purchase #5	$76.40	12.685%	$86.0913	$86.09	$86.10	$86.10
Purchase #6	$12.72	13.621%	$14.4526	$14.45	$14.45	$14.50
Purchase #7	$52.61	13.809%	$59.8749	$59.87	$59.85	$59.90
7 purchase totals =	$335.11		$369.5394	$369.54	$369.55	$369.60