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	$134.56	8.419%	$145.8886	$145.89	$145.90	$145.90
Purchase #2	$189.96	11.339%	$211.4996	$211.50	$211.50	$211.50
Purchase #3	$136.39	6.811%	$145.6795	$145.68	$145.70	$145.70
Purchase #4	$111.33	4.693%	$116.5547	$116.55	$116.55	$116.60
Purchase #5	$62.97	4.688%	$65.922	$65.92	$65.90	$65.90
Purchase #6	$137.46	3.531%	$142.3137	$142.31	$142.30	$142.30
Purchase #7	$240.52	12.444%	$270.4503	$270.45	$270.45	$270.50
7 purchase totals =	$1,013.19		$1,098.3084	$1,098.30	$1,098.30	$1,098.40