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	$127.51	10.686%	$141.1357	$141.14	$141.15	$141.10
Purchase #2	$5.68	13.674%	$6.4567	$6.46	$6.45	$6.50
Purchase #3	$118.57	7.428%	$127.3774	$127.38	$127.40	$127.40
Purchase #4	$220.28	10.520%	$243.4535	$243.45	$243.45	$243.50
Purchase #5	$210.49	13.363%	$238.6178	$238.62	$238.60	$238.60
Purchase #6	$171.28	4.229%	$178.5234	$178.52	$178.50	$178.50
Purchase #7	$31.94	8.372%	$34.614	$34.61	$34.60	$34.60
7 purchase totals =	$885.75		$970.1785	$970.18	$970.15	$970.20