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	$66.40	5.837%	$70.2758	$70.28	$70.30	$70.30
Purchase #2	$140.55	3.239%	$145.1024	$145.10	$145.10	$145.10
Purchase #3	$20.45	4.773%	$21.4261	$21.43	$21.45	$21.40
Purchase #4	$206.43	13.132%	$233.5384	$233.54	$233.55	$233.50
Purchase #5	$112.97	9.375%	$123.5609	$123.56	$123.55	$123.60
Purchase #6	$204.51	5.383%	$215.5188	$215.52	$215.50	$215.50
Purchase #7	$79.39	9.475%	$86.9122	$86.91	$86.90	$86.90
7 purchase totals =	$830.70		$896.3346	$896.34	$896.35	$896.30