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	$96.57	9.219%	$105.4728	$105.47	$105.45	$105.50
Purchase #2	$130.27	7.221%	$139.6768	$139.68	$139.70	$139.70
Purchase #3	$131.78	10.667%	$145.837	$145.84	$145.85	$145.80
Purchase #4	$42.89	12.339%	$48.1822	$48.18	$48.20	$48.20
Purchase #5	$240.43	8.237%	$260.2342	$260.23	$260.25	$260.20
Purchase #6	$151.90	3.685%	$157.4975	$157.50	$157.50	$157.50
Purchase #7	$157.63	9.707%	$172.9311	$172.93	$172.95	$172.90
7 purchase totals =	$951.47		$1,029.8316	$1,029.83	$1,029.90	$1,029.80