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	$188.68	4.653%	$197.4593	$197.46	$197.45	$197.50
Purchase #2	$43.38	13.826%	$49.3777	$49.38	$49.40	$49.40
Purchase #3	$151.48	4.488%	$158.2784	$158.28	$158.30	$158.30
Purchase #4	$165.61	9.209%	$180.861	$180.86	$180.85	$180.90
Purchase #5	$61.50	10.330%	$67.853	$67.85	$67.85	$67.90
Purchase #6	$123.73	12.671%	$139.4078	$139.41	$139.40	$139.40
Purchase #7	$235.27	11.685%	$262.7613	$262.76	$262.75	$262.80
7 purchase totals =	$969.65		$1,055.9985	$1,056.00	$1,056.00	$1,056.20