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	$194.74	7.267%	$208.8918	$208.89	$208.90	$208.90
Purchase #2	$214.30	3.178%	$221.1105	$221.11	$221.10	$221.10
Purchase #3	$184.74	3.116%	$190.4965	$190.50	$190.50	$190.50
Purchase #4	$72.42	6.182%	$76.897	$76.90	$76.90	$76.90
Purchase #5	$108.72	7.413%	$116.7794	$116.78	$116.80	$116.80
Purchase #6	$67.94	6.807%	$72.5647	$72.56	$72.55	$72.60
Purchase #7	$168.41	7.792%	$181.5325	$181.53	$181.55	$181.50
7 purchase totals =	$1,011.27		$1,068.2724	$1,068.27	$1,068.30	$1,068.30