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	$59.32	4.533%	$62.009	$62.01	$62.00	$62.00
Purchase #2	$92.88	12.756%	$104.7278	$104.73	$104.75	$104.70
Purchase #3	$51.77	13.537%	$58.7781	$58.78	$58.80	$58.80
Purchase #4	$110.38	12.797%	$124.5053	$124.51	$124.50	$124.50
Purchase #5	$70.66	9.578%	$77.4278	$77.43	$77.45	$77.40
Purchase #6	$242.46	7.109%	$259.6965	$259.70	$259.70	$259.70
Purchase #7	$95.73	4.858%	$100.3806	$100.38	$100.40	$100.40
7 purchase totals =	$723.20		$787.5251	$787.54	$787.60	$787.50