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	$104.49	9.642%	$114.5649	$114.56	$114.55	$114.60
Purchase #2	$240.46	5.442%	$253.5458	$253.55	$253.55	$253.50
Purchase #3	$247.48	13.570%	$281.063	$281.06	$281.05	$281.10
Purchase #4	$102.69	6.538%	$109.4039	$109.40	$109.40	$109.40
Purchase #5	$19.90	9.788%	$21.8478	$21.85	$21.85	$21.80
Purchase #6	$88.28	12.464%	$99.2832	$99.28	$99.30	$99.30
Purchase #7	$45.77	8.620%	$49.7154	$49.72	$49.70	$49.70
7 purchase totals =	$849.07		$929.4240	$929.42	$929.40	$929.40