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	$224.79	7.474%	$241.5908	$241.59	$241.60	$241.60
Purchase #2	$182.94	13.604%	$207.8272	$207.83	$207.85	$207.80
Purchase #3	$97.32	3.372%	$100.6016	$100.60	$100.60	$100.60
Purchase #4	$156.46	10.472%	$172.8445	$172.84	$172.85	$172.80
Purchase #5	$190.53	5.200%	$200.4376	$200.44	$200.45	$200.40
Purchase #6	$40.32	5.820%	$42.6666	$42.67	$42.65	$42.70
Purchase #7	$84.79	4.772%	$88.8362	$88.84	$88.85	$88.80
7 purchase totals =	$977.15		$1,054.8045	$1,054.81	$1,054.85	$1,054.70