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	$76.87	12.489%	$86.4703	$86.47	$86.45	$86.50
Purchase #2	$177.48	3.620%	$183.9048	$183.90	$183.90	$183.90
Purchase #3	$91.64	13.213%	$103.7484	$103.75	$103.75	$103.70
Purchase #4	$127.61	13.463%	$144.7901	$144.79	$144.80	$144.80
Purchase #5	$94.54	9.459%	$103.4825	$103.48	$103.50	$103.50
Purchase #6	$26.30	5.568%	$27.7644	$27.76	$27.75	$27.80
Purchase #7	$129.58	13.185%	$146.6651	$146.67	$146.65	$146.70
7 purchase totals =	$724.02		$796.8256	$796.82	$796.80	$796.90