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	$73.43	7.297%	$78.7882	$78.79	$78.80	$78.80
Purchase #2	$47.50	12.633%	$53.5007	$53.50	$53.50	$53.50
Purchase #3	$145.76	6.187%	$154.7782	$154.78	$154.80	$154.80
Purchase #4	$33.55	13.571%	$38.1031	$38.10	$38.10	$38.10
Purchase #5	$208.41	11.246%	$231.8478	$231.85	$231.85	$231.80
Purchase #6	$149.46	11.410%	$166.5134	$166.51	$166.50	$166.50
Purchase #7	$157.72	11.606%	$176.025	$176.03	$176.05	$176.00
7 purchase totals =	$815.83		$899.5564	$899.56	$899.60	$899.50