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	$250.91	13.381%	$284.4843	$284.48	$284.50	$284.50
Purchase #2	$74.63	10.198%	$82.2408	$82.24	$82.25	$82.20
Purchase #3	$180.35	6.229%	$191.584	$191.58	$191.60	$191.60
Purchase #4	$176.34	8.647%	$191.5881	$191.59	$191.60	$191.60
Purchase #5	$139.33	10.584%	$154.0767	$154.08	$154.10	$154.10
Purchase #6	$44.53	8.339%	$48.2434	$48.24	$48.25	$48.20
Purchase #7	$126.67	6.119%	$134.4209	$134.42	$134.40	$134.40
7 purchase totals =	$992.76		$1,086.6382	$1,086.63	$1,086.70	$1,086.60