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	$54.59	13.455%	$61.9351	$61.94	$61.95	$61.90
Purchase #2	$27.32	8.124%	$29.5395	$29.54	$29.55	$29.50
Purchase #3	$150.65	11.161%	$167.464	$167.46	$167.45	$167.50
Purchase #4	$204.72	11.142%	$227.5299	$227.53	$227.55	$227.50
Purchase #5	$62.96	11.863%	$70.4289	$70.43	$70.45	$70.40
Purchase #6	$215.35	11.562%	$240.2488	$240.25	$240.25	$240.20
Purchase #7	$74.53	6.764%	$79.5712	$79.57	$79.55	$79.60
7 purchase totals =	$790.12		$876.7174	$876.72	$876.75	$876.60