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	$90.61	7.665%	$97.5553	$97.56	$97.55	$97.60
Purchase #2	$237.28	10.203%	$261.4897	$261.49	$261.50	$261.50
Purchase #3	$45.72	4.852%	$47.9383	$47.94	$47.95	$47.90
Purchase #4	$250.56	12.106%	$280.8928	$280.89	$280.90	$280.90
Purchase #5	$48.33	9.139%	$52.7469	$52.75	$52.75	$52.70
Purchase #6	$186.72	5.378%	$196.7618	$196.76	$196.75	$196.80
Purchase #7	$186.87	3.514%	$193.4366	$193.44	$193.45	$193.40
7 purchase totals =	$1,046.09		$1,130.8214	$1,130.83	$1,130.85	$1,130.80