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	$184.60	7.350%	$198.1681	$198.17	$198.15	$198.20
Purchase #2	$61.32	7.627%	$65.9969	$66.00	$66.00	$66.00
Purchase #3	$123.67	12.832%	$139.5393	$139.54	$139.55	$139.50
Purchase #4	$116.74	13.334%	$132.3061	$132.31	$132.30	$132.30
Purchase #5	$207.43	3.319%	$214.3146	$214.31	$214.30	$214.30
Purchase #6	$57.27	13.186%	$64.8216	$64.82	$64.80	$64.80
Purchase #7	$109.71	12.493%	$123.4161	$123.42	$123.40	$123.40
7 purchase totals =	$860.74		$938.5627	$938.57	$938.50	$938.50