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	$111.67	10.580%	$123.4847	$123.48	$123.50	$123.50
Purchase #2	$87.73	4.778%	$91.9217	$91.92	$91.90	$91.90
Purchase #3	$191.89	3.809%	$199.1991	$199.20	$199.20	$199.20
Purchase #4	$18.72	11.198%	$20.8163	$20.82	$20.80	$20.80
Purchase #5	$196.57	8.274%	$212.8342	$212.83	$212.85	$212.80
Purchase #6	$103.60	7.518%	$111.3886	$111.39	$111.40	$111.40
Purchase #7	$248.54	13.512%	$282.1227	$282.12	$282.10	$282.10
7 purchase totals =	$958.72		$1,041.7673	$1,041.76	$1,041.75	$1,041.70