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	$205.83	10.439%	$227.3166	$227.32	$227.30	$227.30
Purchase #2	$238.46	8.579%	$258.9175	$258.92	$258.90	$258.90
Purchase #3	$153.66	13.478%	$174.3703	$174.37	$174.35	$174.40
Purchase #4	$43.50	13.286%	$49.2794	$49.28	$49.30	$49.30
Purchase #5	$49.54	8.815%	$53.907	$53.91	$53.90	$53.90
Purchase #6	$226.86	12.454%	$255.1131	$255.11	$255.10	$255.10
Purchase #7	$225.78	12.543%	$254.0996	$254.10	$254.10	$254.10
7 purchase totals =	$1,143.63		$1,273.0035	$1,273.01	$1,272.95	$1,273.00