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	$243.44	7.660%	$262.0875	$262.09	$262.10	$262.10
Purchase #2	$244.25	5.689%	$258.1454	$258.15	$258.15	$258.10
Purchase #3	$137.86	7.200%	$147.7859	$147.79	$147.80	$147.80
Purchase #4	$132.57	12.329%	$148.9146	$148.91	$148.90	$148.90
Purchase #5	$94.40	5.188%	$99.2975	$99.30	$99.30	$99.30
Purchase #6	$104.28	13.684%	$118.5497	$118.55	$118.55	$118.50
Purchase #7	$82.60	12.387%	$92.8317	$92.83	$92.85	$92.80
7 purchase totals =	$1,039.40		$1,127.6123	$1,127.62	$1,127.65	$1,127.50