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	$100.86	4.233%	$105.1294	$105.13	$105.15	$105.10
Purchase #2	$192.99	6.695%	$205.9107	$205.91	$205.90	$205.90
Purchase #3	$163.96	11.614%	$183.0023	$183.00	$183.00	$183.00
Purchase #4	$80.62	12.522%	$90.7152	$90.72	$90.70	$90.70
Purchase #5	$94.80	8.187%	$102.5613	$102.56	$102.55	$102.60
Purchase #6	$96.67	7.132%	$103.5645	$103.56	$103.55	$103.60
Purchase #7	$139.70	13.280%	$158.2522	$158.25	$158.25	$158.30
7 purchase totals =	$869.60		$949.1356	$949.13	$949.10	$949.20