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	$38.27	9.335%	$41.8425	$41.84	$41.85	$41.80
Purchase #2	$187.89	11.500%	$209.4974	$209.50	$209.50	$209.50
Purchase #3	$133.45	6.126%	$141.6251	$141.63	$141.65	$141.60
Purchase #4	$248.64	7.810%	$268.0588	$268.06	$268.05	$268.10
Purchase #5	$104.90	11.388%	$116.846	$116.85	$116.85	$116.80
Purchase #6	$37.81	12.530%	$42.5476	$42.55	$42.55	$42.50
Purchase #7	$247.64	12.593%	$278.8253	$278.83	$278.85	$278.80
7 purchase totals =	$998.60		$1,099.2427	$1,099.26	$1,099.30	$1,099.10