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	$52.58	3.256%	$54.292	$54.29	$54.30	$54.30
Purchase #2	$172.64	7.422%	$185.4533	$185.45	$185.45	$185.50
Purchase #3	$127.47	7.763%	$137.3655	$137.37	$137.35	$137.40
Purchase #4	$102.94	6.671%	$109.8071	$109.81	$109.80	$109.80
Purchase #5	$201.50	6.754%	$215.1093	$215.11	$215.10	$215.10
Purchase #6	$225.50	7.733%	$242.9379	$242.94	$242.95	$242.90
Purchase #7	$59.28	12.221%	$66.5246	$66.52	$66.50	$66.50
7 purchase totals =	$941.91		$1,011.4897	$1,011.49	$1,011.45	$1,011.50