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	$162.83	5.767%	$172.2204	$172.22	$172.20	$172.20
Purchase #2	$241.79	13.121%	$273.5153	$273.52	$273.50	$273.50
Purchase #3	$139.91	9.304%	$152.9272	$152.93	$152.95	$152.90
Purchase #4	$248.32	13.115%	$280.8872	$280.89	$280.90	$280.90
Purchase #5	$212.78	5.741%	$224.9957	$225.00	$225.00	$225.00
Purchase #6	$18.42	11.237%	$20.4899	$20.49	$20.50	$20.50
Purchase #7	$134.33	7.675%	$144.6398	$144.64	$144.65	$144.60
7 purchase totals =	$1,158.38		$1,269.6755	$1,269.69	$1,269.70	$1,269.60