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	$139.85	11.361%	$155.7384	$155.74	$155.75	$155.70
Purchase #2	$65.72	10.221%	$72.4372	$72.44	$72.45	$72.40
Purchase #3	$100.60	8.358%	$109.0081	$109.01	$109.00	$109.00
Purchase #4	$144.97	9.632%	$158.9335	$158.93	$158.95	$158.90
Purchase #5	$54.32	4.656%	$56.8491	$56.85	$56.85	$56.80
Purchase #6	$184.70	3.717%	$191.5653	$191.57	$191.55	$191.60
Purchase #7	$136.64	10.645%	$151.1853	$151.19	$151.20	$151.20
7 purchase totals =	$826.80		$895.7169	$895.73	$895.75	$895.60