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	$214.51	11.325%	$238.8033	$238.80	$238.80	$238.80
Purchase #2	$235.77	6.701%	$251.5689	$251.57	$251.55	$251.60
Purchase #3	$50.69	10.720%	$56.124	$56.12	$56.10	$56.10
Purchase #4	$38.74	13.410%	$43.935	$43.94	$43.95	$43.90
Purchase #5	$56.32	9.161%	$61.4795	$61.48	$61.50	$61.50
Purchase #6	$250.66	13.514%	$284.5342	$284.53	$284.55	$284.50
Purchase #7	$44.59	13.465%	$50.594	$50.59	$50.60	$50.60
7 purchase totals =	$891.28		$987.0389	$987.03	$987.05	$987.00