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	$100.87	10.734%	$111.6974	$111.70	$111.70	$111.70
Purchase #2	$171.60	11.354%	$191.0835	$191.08	$191.10	$191.10
Purchase #3	$115.28	3.228%	$119.0012	$119.00	$119.00	$119.00
Purchase #4	$49.79	13.144%	$56.3344	$56.33	$56.35	$56.30
Purchase #5	$78.38	3.822%	$81.3757	$81.38	$81.40	$81.40
Purchase #6	$83.86	11.772%	$93.732	$93.73	$93.75	$93.70
Purchase #7	$7.82	12.844%	$8.8244	$8.82	$8.80	$8.80
7 purchase totals =	$607.60		$662.0486	$662.04	$662.10	$662.00