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	$105.83	8.163%	$114.4689	$114.47	$114.45	$114.50
Purchase #2	$50.72	9.161%	$55.3665	$55.37	$55.35	$55.40
Purchase #3	$36.66	4.706%	$38.3852	$38.39	$38.40	$38.40
Purchase #4	$247.43	5.848%	$261.8997	$261.90	$261.90	$261.90
Purchase #5	$54.57	3.431%	$56.4423	$56.44	$56.45	$56.40
Purchase #6	$95.64	8.203%	$103.4853	$103.49	$103.50	$103.50
Purchase #7	$135.31	11.357%	$150.6772	$150.68	$150.70	$150.70
7 purchase totals =	$726.16		$780.7251	$780.74	$780.75	$780.80