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	$92.42	11.454%	$103.0058	$103.01	$103.00	$103.00
Purchase #2	$106.45	4.711%	$111.4649	$111.46	$111.45	$111.50
Purchase #3	$224.82	12.813%	$253.6262	$253.63	$253.65	$253.60
Purchase #4	$84.88	11.497%	$94.6387	$94.64	$94.65	$94.60
Purchase #5	$41.27	3.301%	$42.6323	$42.63	$42.65	$42.60
Purchase #6	$139.49	11.320%	$155.2803	$155.28	$155.30	$155.30
Purchase #7	$182.25	4.647%	$190.7192	$190.72	$190.70	$190.70
7 purchase totals =	$871.58		$951.3674	$951.37	$951.40	$951.30