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	$210.39	3.620%	$218.0061	$218.01	$218.00	$218.00
Purchase #2	$38.56	10.794%	$42.7222	$42.72	$42.70	$42.70
Purchase #3	$245.35	5.338%	$258.4468	$258.45	$258.45	$258.40
Purchase #4	$96.44	13.704%	$109.6561	$109.66	$109.65	$109.70
Purchase #5	$65.44	7.730%	$70.4985	$70.50	$70.50	$70.50
Purchase #6	$132.27	6.651%	$141.0673	$141.07	$141.05	$141.10
Purchase #7	$57.48	6.563%	$61.2524	$61.25	$61.25	$61.30
7 purchase totals =	$845.93		$901.6494	$901.66	$901.60	$901.70