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	$144.44	5.807%	$152.8276	$152.83	$152.85	$152.80
Purchase #2	$238.60	11.714%	$266.5496	$266.55	$266.55	$266.50
Purchase #3	$117.37	5.420%	$123.7315	$123.73	$123.75	$123.70
Purchase #4	$103.40	6.338%	$109.9535	$109.95	$109.95	$110.00
Purchase #5	$162.98	5.302%	$171.6212	$171.62	$171.60	$171.60
Purchase #6	$158.79	13.556%	$180.3156	$180.32	$180.30	$180.30
Purchase #7	$229.85	10.483%	$253.9452	$253.95	$253.95	$253.90
7 purchase totals =	$1,155.43		$1,258.9442	$1,258.95	$1,258.95	$1,258.80