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	$224.72	9.275%	$245.5628	$245.56	$245.55	$245.60
Purchase #2	$51.86	6.845%	$55.4098	$55.41	$55.40	$55.40
Purchase #3	$22.41	12.119%	$25.1259	$25.13	$25.15	$25.10
Purchase #4	$69.89	12.860%	$78.8779	$78.88	$78.90	$78.90
Purchase #5	$77.70	12.861%	$87.693	$87.69	$87.70	$87.70
Purchase #6	$123.75	6.315%	$131.5648	$131.56	$131.55	$131.60
Purchase #7	$147.79	5.611%	$156.0825	$156.08	$156.10	$156.10
7 purchase totals =	$718.12		$780.3167	$780.31	$780.35	$780.40