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	$104.60	6.156%	$111.0392	$111.04	$111.05	$111.00
Purchase #2	$9.69	11.746%	$10.8282	$10.83	$10.85	$10.80
Purchase #3	$236.54	7.818%	$255.0327	$255.03	$255.05	$255.00
Purchase #4	$175.75	6.305%	$186.831	$186.83	$186.85	$186.80
Purchase #5	$97.75	12.162%	$109.6384	$109.64	$109.65	$109.60
Purchase #6	$5.26	4.755%	$5.5101	$5.51	$5.50	$5.50
Purchase #7	$231.47	3.855%	$240.3932	$240.39	$240.40	$240.40
7 purchase totals =	$861.06		$919.2728	$919.27	$919.35	$919.10