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	$103.64	13.724%	$117.8636	$117.86	$117.85	$117.90
Purchase #2	$219.85	9.419%	$240.5577	$240.56	$240.55	$240.60
Purchase #3	$98.93	3.600%	$102.4915	$102.49	$102.50	$102.50
Purchase #4	$122.60	6.361%	$130.3986	$130.40	$130.40	$130.40
Purchase #5	$99.41	4.256%	$103.6409	$103.64	$103.65	$103.60
Purchase #6	$153.43	9.169%	$167.498	$167.50	$167.50	$167.50
Purchase #7	$199.51	3.440%	$206.3731	$206.37	$206.35	$206.40
7 purchase totals =	$997.37		$1,068.8234	$1,068.82	$1,068.80	$1,068.90