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	$109.50	9.365%	$119.7547	$119.75	$119.75	$119.80
Purchase #2	$159.96	5.853%	$169.3225	$169.32	$169.30	$169.30
Purchase #3	$133.86	12.352%	$150.3944	$150.39	$150.40	$150.40
Purchase #4	$158.43	4.421%	$165.4342	$165.43	$165.45	$165.40
Purchase #5	$118.56	8.808%	$129.0028	$129.00	$129.00	$129.00
Purchase #6	$118.83	11.156%	$132.0867	$132.09	$132.10	$132.10
Purchase #7	$244.37	5.378%	$257.5122	$257.51	$257.50	$257.50
7 purchase totals =	$1,043.51		$1,123.5075	$1,123.49	$1,123.50	$1,123.50