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	$248.56	13.261%	$281.5215	$281.52	$281.50	$281.50
Purchase #2	$82.56	11.504%	$92.0577	$92.06	$92.05	$92.10
Purchase #3	$105.50	12.377%	$118.5577	$118.56	$118.55	$118.60
Purchase #4	$198.66	9.335%	$217.2049	$217.20	$217.20	$217.20
Purchase #5	$154.82	8.777%	$168.4086	$168.41	$168.40	$168.40
Purchase #6	$181.67	12.557%	$204.4823	$204.48	$204.50	$204.50
Purchase #7	$38.65	7.780%	$41.657	$41.66	$41.65	$41.70
7 purchase totals =	$1,010.42		$1,123.8897	$1,123.89	$1,123.85	$1,124.00