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	$167.83	9.785%	$184.2522	$184.25	$184.25	$184.30
Purchase #2	$92.60	13.806%	$105.3844	$105.38	$105.40	$105.40
Purchase #3	$212.31	3.513%	$219.7685	$219.77	$219.75	$219.80
Purchase #4	$237.47	8.545%	$257.7618	$257.76	$257.75	$257.80
Purchase #5	$119.30	9.477%	$130.6061	$130.61	$130.60	$130.60
Purchase #6	$79.73	11.691%	$89.0512	$89.05	$89.05	$89.10
Purchase #7	$47.72	3.815%	$49.5405	$49.54	$49.55	$49.50
7 purchase totals =	$956.96		$1,036.3647	$1,036.36	$1,036.35	$1,036.50