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	$37.60	13.548%	$42.694	$42.69	$42.70	$42.70
Purchase #2	$103.44	7.822%	$111.5311	$111.53	$111.55	$111.50
Purchase #3	$103.67	7.202%	$111.1363	$111.14	$111.15	$111.10
Purchase #4	$238.25	9.582%	$261.0791	$261.08	$261.10	$261.10
Purchase #5	$185.78	11.798%	$207.6983	$207.70	$207.70	$207.70
Purchase #6	$219.90	7.105%	$235.5239	$235.52	$235.50	$235.50
Purchase #7	$96.48	3.142%	$99.5114	$99.51	$99.50	$99.50
7 purchase totals =	$985.12		$1,069.1741	$1,069.17	$1,069.20	$1,069.10