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	$207.35	7.676%	$223.2662	$223.27	$223.25	$223.30
Purchase #2	$216.98	6.143%	$230.3091	$230.31	$230.30	$230.30
Purchase #3	$132.94	3.444%	$137.5185	$137.52	$137.50	$137.50
Purchase #4	$10.82	4.600%	$11.3177	$11.32	$11.30	$11.30
Purchase #5	$153.61	4.577%	$160.6407	$160.64	$160.65	$160.60
Purchase #6	$213.52	6.509%	$227.418	$227.42	$227.40	$227.40
Purchase #7	$26.96	5.842%	$28.535	$28.54	$28.55	$28.50
7 purchase totals =	$962.18		$1,019.0052	$1,019.02	$1,018.95	$1,018.90