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	$54.37	11.378%	$60.5562	$60.56	$60.55	$60.60
Purchase #2	$146.98	7.710%	$158.3122	$158.31	$158.30	$158.30
Purchase #3	$226.65	4.369%	$236.5523	$236.55	$236.55	$236.60
Purchase #4	$88.31	13.520%	$100.2495	$100.25	$100.25	$100.20
Purchase #5	$191.70	12.737%	$216.1168	$216.12	$216.10	$216.10
Purchase #6	$156.53	12.468%	$176.0462	$176.05	$176.05	$176.00
Purchase #7	$103.43	8.236%	$111.9485	$111.95	$111.95	$111.90
7 purchase totals =	$967.97		$1,059.7817	$1,059.79	$1,059.75	$1,059.70