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	$68.85	4.713%	$72.0949	$72.09	$72.10	$72.10
Purchase #2	$16.60	13.382%	$18.8214	$18.82	$18.80	$18.80
Purchase #3	$95.53	10.256%	$105.3276	$105.33	$105.35	$105.30
Purchase #4	$244.44	10.365%	$269.7762	$269.78	$269.80	$269.80
Purchase #5	$214.68	9.345%	$234.7418	$234.74	$234.75	$234.70
Purchase #6	$142.48	12.672%	$160.5351	$160.54	$160.55	$160.50
Purchase #7	$36.69	4.494%	$38.3388	$38.34	$38.35	$38.30
7 purchase totals =	$819.27		$899.6358	$899.64	$899.70	$899.50