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	$79.78	7.808%	$86.0092	$86.01	$86.00	$86.00
Purchase #2	$225.51	13.309%	$255.5231	$255.52	$255.50	$255.50
Purchase #3	$132.30	5.505%	$139.5831	$139.58	$139.60	$139.60
Purchase #4	$144.59	5.765%	$152.9256	$152.93	$152.95	$152.90
Purchase #5	$122.46	6.469%	$130.3819	$130.38	$130.40	$130.40
Purchase #6	$236.85	11.611%	$264.3507	$264.35	$264.35	$264.40
Purchase #7	$220.79	7.125%	$236.5213	$236.52	$236.50	$236.50
7 purchase totals =	$1,162.28		$1,265.2949	$1,265.29	$1,265.30	$1,265.30