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	$168.69	10.611%	$186.5897	$186.59	$186.60	$186.60
Purchase #2	$38.32	13.692%	$43.5668	$43.57	$43.55	$43.60
Purchase #3	$186.52	4.466%	$194.85	$194.85	$194.85	$194.90
Purchase #4	$140.29	11.479%	$156.3939	$156.39	$156.40	$156.40
Purchase #5	$154.51	6.424%	$164.4357	$164.44	$164.45	$164.40
Purchase #6	$246.51	12.829%	$278.1348	$278.13	$278.15	$278.10
Purchase #7	$106.84	13.489%	$121.2516	$121.25	$121.25	$121.30
7 purchase totals =	$1,041.68		$1,145.2225	$1,145.22	$1,145.25	$1,145.30