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	$244.86	4.410%	$255.6583	$255.66	$255.65	$255.70
Purchase #2	$65.88	7.364%	$70.7314	$70.73	$70.75	$70.70
Purchase #3	$191.58	13.180%	$216.8302	$216.83	$216.85	$216.80
Purchase #4	$227.35	3.350%	$234.9662	$234.97	$234.95	$235.00
Purchase #5	$180.32	6.387%	$191.837	$191.84	$191.85	$191.80
Purchase #6	$38.49	10.752%	$42.6284	$42.63	$42.65	$42.60
Purchase #7	$66.73	7.811%	$71.9423	$71.94	$71.95	$71.90
7 purchase totals =	$1,015.21		$1,084.5938	$1,084.60	$1,084.65	$1,084.50