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	$185.57	10.522%	$205.0957	$205.10	$205.10	$205.10
Purchase #2	$191.80	13.422%	$217.5434	$217.54	$217.55	$217.50
Purchase #3	$127.95	10.344%	$141.1851	$141.19	$141.20	$141.20
Purchase #4	$150.65	7.790%	$162.3856	$162.39	$162.40	$162.40
Purchase #5	$5.82	10.128%	$6.4094	$6.41	$6.40	$6.40
Purchase #6	$37.46	8.659%	$40.7037	$40.70	$40.70	$40.70
Purchase #7	$238.42	3.378%	$246.4738	$246.47	$246.45	$246.50
7 purchase totals =	$937.67		$1,019.7967	$1,019.80	$1,019.80	$1,019.80