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	$180.87	3.271%	$186.7863	$186.79	$186.80	$186.80
Purchase #2	$196.52	10.612%	$217.3747	$217.37	$217.35	$217.40
Purchase #3	$182.70	7.618%	$196.6181	$196.62	$196.60	$196.60
Purchase #4	$42.98	4.558%	$44.939	$44.94	$44.95	$44.90
Purchase #5	$64.28	13.455%	$72.9289	$72.93	$72.95	$72.90
Purchase #6	$62.72	11.514%	$69.9416	$69.94	$69.95	$69.90
Purchase #7	$228.30	4.173%	$237.827	$237.83	$237.85	$237.80
7 purchase totals =	$958.37		$1,026.4156	$1,026.42	$1,026.45	$1,026.30