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	$126.65	5.426%	$133.522	$133.52	$133.50	$133.50
Purchase #2	$189.69	7.382%	$203.6929	$203.69	$203.70	$203.70
Purchase #3	$242.72	3.348%	$250.8463	$250.85	$250.85	$250.80
Purchase #4	$45.80	13.200%	$51.8456	$51.85	$51.85	$51.80
Purchase #5	$101.27	8.210%	$109.5843	$109.58	$109.60	$109.60
Purchase #6	$172.81	7.598%	$185.9401	$185.94	$185.95	$185.90
Purchase #7	$56.47	5.635%	$59.6521	$59.65	$59.65	$59.70
7 purchase totals =	$935.41		$995.0833	$995.08	$995.10	$995.00