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	$128.78	12.721%	$145.1621	$145.16	$145.15	$145.20
Purchase #2	$191.83	5.304%	$202.0047	$202.00	$202.00	$202.00
Purchase #3	$133.46	5.832%	$141.2434	$141.24	$141.25	$141.20
Purchase #4	$98.67	13.372%	$111.8642	$111.86	$111.85	$111.90
Purchase #5	$66.78	12.188%	$74.9191	$74.92	$74.90	$74.90
Purchase #6	$102.31	11.844%	$114.4276	$114.43	$114.45	$114.40
Purchase #7	$79.30	9.538%	$86.8636	$86.86	$86.85	$86.90
7 purchase totals =	$801.13		$876.4847	$876.47	$876.45	$876.50