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	$226.51	11.139%	$251.7409	$251.74	$251.75	$251.70
Purchase #2	$174.32	12.771%	$196.5824	$196.58	$196.60	$196.60
Purchase #3	$126.98	3.335%	$131.2148	$131.21	$131.20	$131.20
Purchase #4	$158.68	10.827%	$175.8603	$175.86	$175.85	$175.90
Purchase #5	$176.75	11.398%	$196.896	$196.90	$196.90	$196.90
Purchase #6	$21.68	3.546%	$22.4488	$22.45	$22.45	$22.40
Purchase #7	$77.80	8.134%	$84.1283	$84.13	$84.15	$84.10
7 purchase totals =	$962.72		$1,058.8715	$1,058.87	$1,058.90	$1,058.80