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	$136.96	5.385%	$144.3353	$144.34	$144.35	$144.30
Purchase #2	$54.41	13.669%	$61.8473	$61.85	$61.85	$61.80
Purchase #3	$95.93	13.591%	$108.9678	$108.97	$108.95	$109.00
Purchase #4	$199.83	8.532%	$216.8795	$216.88	$216.90	$216.90
Purchase #5	$178.97	6.424%	$190.467	$190.47	$190.45	$190.50
Purchase #6	$152.47	7.233%	$163.4982	$163.50	$163.50	$163.50
Purchase #7	$221.83	9.493%	$242.8883	$242.89	$242.90	$242.90
7 purchase totals =	$1,040.40		$1,128.8834	$1,128.90	$1,128.90	$1,128.90