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	$168.38	6.146%	$178.7286	$178.73	$178.75	$178.70
Purchase #2	$30.91	13.706%	$35.1465	$35.15	$35.15	$35.10
Purchase #3	$187.34	9.427%	$205.0005	$205.00	$205.00	$205.00
Purchase #4	$82.52	5.233%	$86.8383	$86.84	$86.85	$86.80
Purchase #5	$241.56	5.102%	$253.8844	$253.88	$253.90	$253.90
Purchase #6	$131.83	9.446%	$144.2827	$144.28	$144.30	$144.30
Purchase #7	$132.69	9.150%	$144.8311	$144.83	$144.85	$144.80
7 purchase totals =	$975.23		$1,048.7121	$1,048.71	$1,048.80	$1,048.60