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	$169.30	4.164%	$176.3497	$176.35	$176.35	$176.30
Purchase #2	$116.97	10.219%	$128.9232	$128.92	$128.90	$128.90
Purchase #3	$211.77	9.270%	$231.4011	$231.40	$231.40	$231.40
Purchase #4	$61.38	7.358%	$65.8963	$65.90	$65.90	$65.90
Purchase #5	$69.71	4.307%	$72.7124	$72.71	$72.70	$72.70
Purchase #6	$104.52	3.680%	$108.3663	$108.37	$108.35	$108.40
Purchase #7	$110.67	11.224%	$123.0916	$123.09	$123.10	$123.10
7 purchase totals =	$844.32		$906.7406	$906.74	$906.70	$906.70