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	$56.47	5.763%	$59.7244	$59.72	$59.70	$59.70
Purchase #2	$164.45	9.296%	$179.7373	$179.74	$179.75	$179.70
Purchase #3	$175.30	6.805%	$187.2292	$187.23	$187.25	$187.20
Purchase #4	$247.88	11.758%	$277.0257	$277.03	$277.05	$277.00
Purchase #5	$86.75	4.187%	$90.3822	$90.38	$90.40	$90.40
Purchase #6	$117.49	5.615%	$124.0871	$124.09	$124.10	$124.10
Purchase #7	$179.59	11.280%	$199.8478	$199.85	$199.85	$199.80
7 purchase totals =	$1,027.93		$1,118.0337	$1,118.04	$1,118.10	$1,117.90