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	$91.68	4.622%	$95.9174	$95.92	$95.90	$95.90
Purchase #2	$220.40	13.542%	$250.2466	$250.25	$250.25	$250.20
Purchase #3	$224.39	7.526%	$241.2776	$241.28	$241.30	$241.30
Purchase #4	$103.81	7.755%	$111.8605	$111.86	$111.85	$111.90
Purchase #5	$231.47	4.809%	$242.6014	$242.60	$242.60	$242.60
Purchase #6	$110.28	5.721%	$116.5891	$116.59	$116.60	$116.60
Purchase #7	$239.52	5.775%	$253.3523	$253.35	$253.35	$253.40
7 purchase totals =	$1,221.55		$1,311.8449	$1,311.85	$1,311.85	$1,311.90