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	$38.64	10.874%	$42.8417	$42.84	$42.85	$42.80
Purchase #2	$54.42	11.722%	$60.7991	$60.80	$60.80	$60.80
Purchase #3	$73.65	11.770%	$82.3186	$82.32	$82.30	$82.30
Purchase #4	$156.84	9.651%	$171.9766	$171.98	$172.00	$172.00
Purchase #5	$180.90	3.463%	$187.1646	$187.16	$187.15	$187.20
Purchase #6	$184.75	13.593%	$209.8631	$209.86	$209.85	$209.90
Purchase #7	$205.38	13.242%	$232.5764	$232.58	$232.60	$232.60
7 purchase totals =	$894.58		$987.5401	$987.54	$987.55	$987.60