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	$129.79	4.836%	$136.0666	$136.07	$136.05	$136.10
Purchase #2	$160.68	4.866%	$168.4987	$168.50	$168.50	$168.50
Purchase #3	$48.85	7.657%	$52.5904	$52.59	$52.60	$52.60
Purchase #4	$89.95	10.271%	$99.1888	$99.19	$99.20	$99.20
Purchase #5	$215.42	3.296%	$222.5202	$222.52	$222.50	$222.50
Purchase #6	$29.46	12.466%	$33.1325	$33.13	$33.15	$33.10
Purchase #7	$100.55	11.388%	$112.0006	$112.00	$112.00	$112.00
7 purchase totals =	$774.70		$823.9978	$824.00	$824.00	$824.00