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	$160.53	9.759%	$176.1961	$176.20	$176.20	$176.20
Purchase #2	$199.60	12.486%	$224.5221	$224.52	$224.50	$224.50
Purchase #3	$147.45	7.373%	$158.3215	$158.32	$158.30	$158.30
Purchase #4	$210.30	6.830%	$224.6635	$224.66	$224.65	$224.70
Purchase #5	$95.31	4.488%	$99.5875	$99.59	$99.60	$99.60
Purchase #6	$79.43	9.291%	$86.8098	$86.81	$86.80	$86.80
Purchase #7	$129.71	9.867%	$142.5085	$142.51	$142.50	$142.50
7 purchase totals =	$1,022.33		$1,112.6090	$1,112.61	$1,112.55	$1,112.60