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	$22.92	7.466%	$24.6312	$24.63	$24.65	$24.60
Purchase #2	$30.90	6.497%	$32.9076	$32.91	$32.90	$32.90
Purchase #3	$166.52	9.584%	$182.4793	$182.48	$182.50	$182.50
Purchase #4	$46.55	13.661%	$52.9092	$52.91	$52.90	$52.90
Purchase #5	$84.78	4.414%	$88.5222	$88.52	$88.50	$88.50
Purchase #6	$27.98	7.521%	$30.0844	$30.08	$30.10	$30.10
Purchase #7	$29.29	9.184%	$31.98	$31.98	$32.00	$32.00
7 purchase totals =	$408.94		$443.5139	$443.51	$443.55	$443.50