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	$121.28	9.528%	$132.8356	$132.84	$132.85	$132.80
Purchase #2	$201.72	10.394%	$222.6868	$222.69	$222.70	$222.70
Purchase #3	$166.85	8.848%	$181.6129	$181.61	$181.60	$181.60
Purchase #4	$176.77	3.826%	$183.5332	$183.53	$183.55	$183.50
Purchase #5	$96.85	10.816%	$107.3253	$107.33	$107.35	$107.30
Purchase #6	$189.76	3.572%	$196.5382	$196.54	$196.55	$196.50
Purchase #7	$105.55	11.206%	$117.3779	$117.38	$117.40	$117.40
7 purchase totals =	$1,058.78		$1,141.9099	$1,141.92	$1,142.00	$1,141.80