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	$247.41	4.833%	$259.3673	$259.37	$259.35	$259.40
Purchase #2	$36.63	13.745%	$41.6648	$41.66	$41.65	$41.70
Purchase #3	$149.70	11.544%	$166.9814	$166.98	$167.00	$167.00
Purchase #4	$68.35	5.440%	$72.0682	$72.07	$72.05	$72.10
Purchase #5	$228.40	7.734%	$246.0645	$246.06	$246.05	$246.10
Purchase #6	$182.83	9.142%	$199.5443	$199.54	$199.55	$199.50
Purchase #7	$131.83	7.496%	$141.712	$141.71	$141.70	$141.70
7 purchase totals =	$1,045.15		$1,127.4025	$1,127.39	$1,127.35	$1,127.50