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	$215.75	4.140%	$224.6821	$224.68	$224.70	$224.70
Purchase #2	$178.47	3.405%	$184.5469	$184.55	$184.55	$184.50
Purchase #3	$249.29	3.827%	$258.8303	$258.83	$258.85	$258.80
Purchase #4	$80.86	10.395%	$89.2654	$89.27	$89.25	$89.30
Purchase #5	$26.92	5.610%	$28.4302	$28.43	$28.45	$28.40
Purchase #6	$150.86	6.139%	$160.1213	$160.12	$160.10	$160.10
Purchase #7	$208.38	13.481%	$236.4717	$236.47	$236.45	$236.50
7 purchase totals =	$1,110.53		$1,182.3479	$1,182.35	$1,182.35	$1,182.30