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	$43.61	10.751%	$48.2985	$48.30	$48.30	$48.30
Purchase #2	$142.26	9.384%	$155.6097	$155.61	$155.60	$155.60
Purchase #3	$89.94	11.661%	$100.4279	$100.43	$100.45	$100.40
Purchase #4	$87.94	9.241%	$96.0665	$96.07	$96.05	$96.10
Purchase #5	$54.55	10.175%	$60.1005	$60.10	$60.10	$60.10
Purchase #6	$189.58	10.505%	$209.4954	$209.50	$209.50	$209.50
Purchase #7	$15.37	12.334%	$17.2657	$17.27	$17.25	$17.30
7 purchase totals =	$623.25		$687.2642	$687.28	$687.25	$687.30