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	$114.47	13.866%	$130.3424	$130.34	$130.35	$130.30
Purchase #2	$52.68	13.626%	$59.8582	$59.86	$59.85	$59.90
Purchase #3	$220.65	7.182%	$236.4971	$236.50	$236.50	$236.50
Purchase #4	$98.51	3.250%	$101.7116	$101.71	$101.70	$101.70
Purchase #5	$157.82	4.502%	$164.9251	$164.93	$164.95	$164.90
Purchase #6	$134.39	6.848%	$143.593	$143.59	$143.60	$143.60
Purchase #7	$197.36	12.174%	$221.3866	$221.39	$221.40	$221.40
7 purchase totals =	$975.88		$1,058.3140	$1,058.32	$1,058.35	$1,058.30