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	$177.80	4.475%	$185.7566	$185.76	$185.75	$185.80
Purchase #2	$139.56	11.847%	$156.0937	$156.09	$156.10	$156.10
Purchase #3	$154.38	6.278%	$164.072	$164.07	$164.05	$164.10
Purchase #4	$179.90	3.818%	$186.7686	$186.77	$186.75	$186.80
Purchase #5	$176.69	7.862%	$190.5814	$190.58	$190.60	$190.60
Purchase #6	$152.41	7.633%	$164.0435	$164.04	$164.05	$164.00
Purchase #7	$90.80	6.480%	$96.6838	$96.68	$96.70	$96.70
7 purchase totals =	$1,071.54		$1,143.9996	$1,143.99	$1,144.00	$1,144.10