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	$72.54	12.750%	$81.7889	$81.79	$81.80	$81.80
Purchase #2	$147.44	5.455%	$155.4829	$155.48	$155.50	$155.50
Purchase #3	$164.85	5.590%	$174.0651	$174.07	$174.05	$174.10
Purchase #4	$59.97	12.228%	$67.3031	$67.30	$67.30	$67.30
Purchase #5	$196.56	12.357%	$220.8489	$220.85	$220.85	$220.80
Purchase #6	$105.93	4.866%	$111.0846	$111.08	$111.10	$111.10
Purchase #7	$158.80	5.638%	$167.7531	$167.75	$167.75	$167.80
7 purchase totals =	$906.09		$978.3266	$978.32	$978.35	$978.40