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	$82.66	10.823%	$91.6063	$91.61	$91.60	$91.60
Purchase #2	$43.87	10.198%	$48.3439	$48.34	$48.35	$48.30
Purchase #3	$202.76	12.429%	$227.961	$227.96	$227.95	$228.00
Purchase #4	$87.88	3.341%	$90.8161	$90.82	$90.80	$90.80
Purchase #5	$127.70	3.199%	$131.7851	$131.79	$131.80	$131.80
Purchase #6	$145.92	11.407%	$162.5651	$162.57	$162.55	$162.60
Purchase #7	$183.78	13.689%	$208.9376	$208.94	$208.95	$208.90
7 purchase totals =	$874.57		$962.0151	$962.03	$962.00	$962.00