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	$103.29	10.524%	$114.1602	$114.16	$114.15	$114.20
Purchase #2	$191.78	12.136%	$215.0544	$215.05	$215.05	$215.10
Purchase #3	$101.31	3.807%	$105.1669	$105.17	$105.15	$105.20
Purchase #4	$53.51	5.825%	$56.627	$56.63	$56.65	$56.60
Purchase #5	$110.59	7.363%	$118.7327	$118.73	$118.75	$118.70
Purchase #6	$145.93	4.247%	$152.1276	$152.13	$152.15	$152.10
Purchase #7	$50.67	6.733%	$54.0816	$54.08	$54.10	$54.10
7 purchase totals =	$757.08		$815.9504	$815.95	$816.00	$816.00