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	$207.70	5.837%	$219.8234	$219.82	$219.80	$219.80
Purchase #2	$93.31	6.243%	$99.1353	$99.14	$99.15	$99.10
Purchase #3	$207.61	4.569%	$217.0957	$217.10	$217.10	$217.10
Purchase #4	$124.66	13.567%	$141.5726	$141.57	$141.55	$141.60
Purchase #5	$202.96	9.638%	$222.5213	$222.52	$222.50	$222.50
Purchase #6	$190.28	13.417%	$215.8099	$215.81	$215.80	$215.80
Purchase #7	$44.68	4.253%	$46.5802	$46.58	$46.60	$46.60
7 purchase totals =	$1,071.20		$1,162.5384	$1,162.54	$1,162.50	$1,162.50