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	$140.36	6.130%	$148.9641	$148.96	$148.95	$149.00
Purchase #2	$123.43	3.495%	$127.7439	$127.74	$127.75	$127.70
Purchase #3	$27.76	13.291%	$31.4496	$31.45	$31.45	$31.40
Purchase #4	$222.95	6.612%	$237.6915	$237.69	$237.70	$237.70
Purchase #5	$94.53	7.303%	$101.4335	$101.43	$101.45	$101.40
Purchase #6	$226.87	6.111%	$240.734	$240.73	$240.75	$240.70
Purchase #7	$133.61	7.431%	$143.5386	$143.54	$143.55	$143.50
7 purchase totals =	$969.51		$1,031.5552	$1,031.54	$1,031.60	$1,031.40