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	$222.84	7.499%	$239.5508	$239.55	$239.55	$239.60
Purchase #2	$95.73	10.538%	$105.818	$105.82	$105.80	$105.80
Purchase #3	$130.89	5.358%	$137.9031	$137.90	$137.90	$137.90
Purchase #4	$22.99	4.309%	$23.9806	$23.98	$24.00	$24.00
Purchase #5	$225.86	7.779%	$243.4296	$243.43	$243.45	$243.40
Purchase #6	$197.63	12.773%	$222.8733	$222.87	$222.85	$222.90
Purchase #7	$66.81	7.733%	$71.9764	$71.98	$72.00	$72.00
7 purchase totals =	$962.75		$1,045.5318	$1,045.53	$1,045.55	$1,045.60