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	$65.42	3.317%	$67.59	$67.59	$67.60	$67.60
Purchase #2	$30.90	9.723%	$33.9044	$33.90	$33.90	$33.90
Purchase #3	$72.98	4.157%	$76.0138	$76.01	$76.00	$76.00
Purchase #4	$59.38	5.195%	$62.4648	$62.46	$62.45	$62.50
Purchase #5	$19.30	3.213%	$19.9201	$19.92	$19.90	$19.90
Purchase #6	$231.59	4.862%	$242.8499	$242.85	$242.85	$242.80
Purchase #7	$101.78	11.593%	$113.5794	$113.58	$113.60	$113.60
7 purchase totals =	$581.35		$616.3224	$616.31	$616.30	$616.30