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	$95.38	10.161%	$105.0716	$105.07	$105.05	$105.10
Purchase #2	$199.39	10.558%	$220.4416	$220.44	$220.45	$220.40
Purchase #3	$36.78	5.695%	$38.8746	$38.87	$38.85	$38.90
Purchase #4	$73.83	12.843%	$83.312	$83.31	$83.30	$83.30
Purchase #5	$22.32	10.235%	$24.6045	$24.60	$24.60	$24.60
Purchase #6	$248.87	9.208%	$271.7859	$271.79	$271.80	$271.80
Purchase #7	$102.54	6.745%	$109.4563	$109.46	$109.45	$109.50
7 purchase totals =	$779.11		$853.5465	$853.54	$853.50	$853.60