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	$242.85	7.682%	$261.5057	$261.51	$261.50	$261.50
Purchase #2	$228.50	12.377%	$256.7814	$256.78	$256.80	$256.80
Purchase #3	$98.81	12.727%	$111.3855	$111.39	$111.40	$111.40
Purchase #4	$28.97	13.613%	$32.9137	$32.91	$32.90	$32.90
Purchase #5	$166.73	12.144%	$186.9777	$186.98	$187.00	$187.00
Purchase #6	$176.27	5.499%	$185.9631	$185.96	$185.95	$186.00
Purchase #7	$167.78	6.597%	$178.8484	$178.85	$178.85	$178.80
7 purchase totals =	$1,109.91		$1,214.3755	$1,214.38	$1,214.40	$1,214.40