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	$230.72	10.648%	$255.2871	$255.29	$255.30	$255.30
Purchase #2	$197.45	7.746%	$212.7445	$212.74	$212.75	$212.70
Purchase #3	$96.89	7.434%	$104.0928	$104.09	$104.10	$104.10
Purchase #4	$70.67	4.136%	$73.5929	$73.59	$73.60	$73.60
Purchase #5	$99.32	4.248%	$103.5391	$103.54	$103.55	$103.50
Purchase #6	$152.38	7.161%	$163.2919	$163.29	$163.30	$163.30
Purchase #7	$243.38	6.480%	$259.151	$259.15	$259.15	$259.20
7 purchase totals =	$1,090.81		$1,171.6993	$1,171.69	$1,171.75	$1,171.70