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	$145.81	4.559%	$152.4575	$152.46	$152.45	$152.50
Purchase #2	$145.97	8.828%	$158.8562	$158.86	$158.85	$158.90
Purchase #3	$224.99	8.579%	$244.2919	$244.29	$244.30	$244.30
Purchase #4	$84.53	6.760%	$90.2442	$90.24	$90.25	$90.20
Purchase #5	$97.65	12.470%	$109.827	$109.83	$109.85	$109.80
Purchase #6	$238.52	11.684%	$266.3887	$266.39	$266.40	$266.40
Purchase #7	$91.28	8.357%	$98.9083	$98.91	$98.90	$98.90
7 purchase totals =	$1,028.75		$1,120.9738	$1,120.98	$1,121.00	$1,121.00