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	$172.63	13.860%	$196.5565	$196.56	$196.55	$196.60
Purchase #2	$66.84	4.818%	$70.0604	$70.06	$70.05	$70.10
Purchase #3	$168.81	10.301%	$186.1991	$186.20	$186.20	$186.20
Purchase #4	$60.25	4.337%	$62.863	$62.86	$62.85	$62.90
Purchase #5	$117.61	6.479%	$125.23	$125.23	$125.25	$125.20
Purchase #6	$74.76	4.458%	$78.0928	$78.09	$78.10	$78.10
Purchase #7	$169.66	11.105%	$188.5007	$188.50	$188.50	$188.50
7 purchase totals =	$830.56		$907.5025	$907.50	$907.50	$907.60