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	$145.90	12.575%	$164.2469	$164.25	$164.25	$164.20
Purchase #2	$25.44	9.754%	$27.9214	$27.92	$27.90	$27.90
Purchase #3	$40.98	5.831%	$43.3695	$43.37	$43.35	$43.40
Purchase #4	$57.31	3.379%	$59.2465	$59.25	$59.25	$59.20
Purchase #5	$72.76	5.305%	$76.6199	$76.62	$76.60	$76.60
Purchase #6	$206.85	6.815%	$220.9468	$220.95	$220.95	$220.90
Purchase #7	$154.65	8.289%	$167.4689	$167.47	$167.45	$167.50
7 purchase totals =	$703.89		$759.8199	$759.83	$759.75	$759.70