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	$71.93	6.635%	$76.7026	$76.70	$76.70	$76.70
Purchase #2	$100.31	11.515%	$111.8607	$111.86	$111.85	$111.90
Purchase #3	$40.94	4.427%	$42.7524	$42.75	$42.75	$42.80
Purchase #4	$200.82	9.131%	$219.1569	$219.16	$219.15	$219.20
Purchase #5	$58.65	12.526%	$65.9965	$66.00	$66.00	$66.00
Purchase #6	$187.78	7.655%	$202.1546	$202.15	$202.15	$202.20
Purchase #7	$31.42	6.389%	$33.4274	$33.43	$33.45	$33.40
7 purchase totals =	$691.85		$752.0511	$752.05	$752.05	$752.20