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	$30.94	5.402%	$32.6114	$32.61	$32.60	$32.60
Purchase #2	$191.86	4.556%	$200.6011	$200.60	$200.60	$200.60
Purchase #3	$215.49	13.409%	$244.3851	$244.39	$244.40	$244.40
Purchase #4	$249.38	9.323%	$272.6297	$272.63	$272.65	$272.60
Purchase #5	$56.63	6.676%	$60.4106	$60.41	$60.40	$60.40
Purchase #6	$227.86	13.215%	$257.9717	$257.97	$257.95	$258.00
Purchase #7	$104.48	6.605%	$111.3809	$111.38	$111.40	$111.40
7 purchase totals =	$1,076.64		$1,179.9905	$1,179.99	$1,180.00	$1,180.00