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	$231.72	6.355%	$246.4458	$246.45	$246.45	$246.40
Purchase #2	$107.95	9.423%	$118.1221	$118.12	$118.10	$118.10
Purchase #3	$135.87	12.161%	$152.3932	$152.39	$152.40	$152.40
Purchase #4	$151.43	8.677%	$164.5696	$164.57	$164.55	$164.60
Purchase #5	$89.86	6.725%	$95.9031	$95.90	$95.90	$95.90
Purchase #6	$164.86	6.419%	$175.4424	$175.44	$175.45	$175.40
Purchase #7	$76.84	8.675%	$83.5059	$83.51	$83.50	$83.50
7 purchase totals =	$958.53		$1,036.3821	$1,036.38	$1,036.35	$1,036.30