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	$217.30	7.441%	$233.4693	$233.47	$233.45	$233.50
Purchase #2	$84.65	12.240%	$95.0112	$95.01	$95.00	$95.00
Purchase #3	$47.75	3.521%	$49.4313	$49.43	$49.45	$49.40
Purchase #4	$196.76	10.192%	$216.8138	$216.81	$216.80	$216.80
Purchase #5	$139.83	11.144%	$155.4127	$155.41	$155.40	$155.40
Purchase #6	$69.74	12.783%	$78.6549	$78.65	$78.65	$78.70
Purchase #7	$126.76	3.410%	$131.0825	$131.08	$131.10	$131.10
7 purchase totals =	$882.79		$959.8757	$959.86	$959.85	$959.90