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	$7.97	5.812%	$8.4332	$8.43	$8.45	$8.40
Purchase #2	$86.44	3.530%	$89.4913	$89.49	$89.50	$89.50
Purchase #3	$89.31	6.684%	$95.2795	$95.28	$95.30	$95.30
Purchase #4	$155.38	12.379%	$174.6145	$174.61	$174.60	$174.60
Purchase #5	$46.71	4.470%	$48.7979	$48.80	$48.80	$48.80
Purchase #6	$53.25	11.722%	$59.492	$59.49	$59.50	$59.50
Purchase #7	$20.99	7.676%	$22.6012	$22.60	$22.60	$22.60
7 purchase totals =	$460.05		$498.7096	$498.70	$498.75	$498.70