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	$144.38	13.486%	$163.8511	$163.85	$163.85	$163.90
Purchase #2	$172.61	7.569%	$185.6749	$185.67	$185.65	$185.70
Purchase #3	$182.43	4.328%	$190.3256	$190.33	$190.35	$190.30
Purchase #4	$137.71	6.151%	$146.1805	$146.18	$146.20	$146.20
Purchase #5	$162.69	10.214%	$179.3072	$179.31	$179.30	$179.30
Purchase #6	$38.46	5.618%	$40.6207	$40.62	$40.60	$40.60
Purchase #7	$120.80	6.188%	$128.2751	$128.28	$128.30	$128.30
7 purchase totals =	$959.08		$1,034.2351	$1,034.24	$1,034.25	$1,034.30