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	$128.87	9.141%	$140.65	$140.65	$140.65	$140.70
Purchase #2	$91.70	3.693%	$95.0865	$95.09	$95.10	$95.10
Purchase #3	$147.76	4.705%	$154.7121	$154.71	$154.70	$154.70
Purchase #4	$139.50	8.607%	$151.5068	$151.51	$151.50	$151.50
Purchase #5	$18.74	11.140%	$20.8276	$20.83	$20.85	$20.80
Purchase #6	$87.39	7.729%	$94.1444	$94.14	$94.15	$94.10
Purchase #7	$177.39	5.744%	$187.5793	$187.58	$187.60	$187.60
7 purchase totals =	$791.35		$844.5067	$844.51	$844.55	$844.50