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	$65.87	9.440%	$72.0881	$72.09	$72.10	$72.10
Purchase #2	$22.66	3.874%	$23.5378	$23.54	$23.55	$23.50
Purchase #3	$31.46	4.199%	$32.781	$32.78	$32.80	$32.80
Purchase #4	$103.30	6.812%	$110.3368	$110.34	$110.35	$110.30
Purchase #5	$131.60	4.538%	$137.572	$137.57	$137.55	$137.60
Purchase #6	$245.93	5.744%	$260.0562	$260.06	$260.05	$260.10
Purchase #7	$158.97	3.485%	$164.5101	$164.51	$164.50	$164.50
7 purchase totals =	$759.79		$800.8820	$800.89	$800.90	$800.90