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	$226.67	5.160%	$238.3662	$238.37	$238.35	$238.40
Purchase #2	$165.86	11.607%	$185.1114	$185.11	$185.10	$185.10
Purchase #3	$103.82	12.389%	$116.6823	$116.68	$116.70	$116.70
Purchase #4	$133.60	10.721%	$147.9233	$147.92	$147.90	$147.90
Purchase #5	$116.63	10.291%	$128.6324	$128.63	$128.65	$128.60
Purchase #6	$52.47	13.688%	$59.6521	$59.65	$59.65	$59.70
Purchase #7	$187.31	12.789%	$211.2651	$211.27	$211.25	$211.30
7 purchase totals =	$986.36		$1,087.6328	$1,087.63	$1,087.60	$1,087.70