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	$106.60	4.694%	$111.6038	$111.60	$111.60	$111.60
Purchase #2	$25.91	11.613%	$28.9189	$28.92	$28.90	$28.90
Purchase #3	$104.64	8.484%	$113.5177	$113.52	$113.50	$113.50
Purchase #4	$235.67	11.130%	$261.9001	$261.90	$261.90	$261.90
Purchase #5	$45.45	6.813%	$48.5465	$48.55	$48.55	$48.50
Purchase #6	$181.53	6.372%	$193.0971	$193.10	$193.10	$193.10
Purchase #7	$97.26	4.807%	$101.9353	$101.94	$101.95	$101.90
7 purchase totals =	$797.06		$859.5194	$859.53	$859.50	$859.40