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	$82.42	6.252%	$87.5729	$87.57	$87.55	$87.60
Purchase #2	$84.97	7.786%	$91.5858	$91.59	$91.60	$91.60
Purchase #3	$87.62	4.784%	$91.8117	$91.81	$91.80	$91.80
Purchase #4	$211.74	13.165%	$239.6156	$239.62	$239.60	$239.60
Purchase #5	$41.55	12.172%	$46.6075	$46.61	$46.60	$46.60
Purchase #6	$77.43	7.297%	$83.0801	$83.08	$83.10	$83.10
Purchase #7	$69.77	3.539%	$72.2392	$72.24	$72.25	$72.20
7 purchase totals =	$655.50		$712.5128	$712.52	$712.50	$712.50