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	$229.69	5.108%	$241.4226	$241.42	$241.40	$241.40
Purchase #2	$239.29	6.866%	$255.7197	$255.72	$255.70	$255.70
Purchase #3	$168.59	3.465%	$174.4316	$174.43	$174.45	$174.40
Purchase #4	$108.34	8.527%	$117.5782	$117.58	$117.60	$117.60
Purchase #5	$221.43	10.598%	$244.8972	$244.90	$244.90	$244.90
Purchase #6	$218.82	3.398%	$226.2555	$226.26	$226.25	$226.30
Purchase #7	$228.94	5.204%	$240.854	$240.85	$240.85	$240.90
7 purchase totals =	$1,415.10		$1,501.1588	$1,501.16	$1,501.15	$1,501.20