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	$142.61	5.870%	$150.9812	$150.98	$151.00	$151.00
Purchase #2	$46.31	4.726%	$48.4986	$48.50	$48.50	$48.50
Purchase #3	$27.79	13.280%	$31.4805	$31.48	$31.50	$31.50
Purchase #4	$173.27	10.727%	$191.8567	$191.86	$191.85	$191.90
Purchase #5	$11.27	3.416%	$11.655	$11.66	$11.65	$11.70
Purchase #6	$116.84	11.386%	$130.1434	$130.14	$130.15	$130.10
Purchase #7	$97.35	10.792%	$107.856	$107.86	$107.85	$107.90
7 purchase totals =	$615.44		$672.4714	$672.48	$672.50	$672.60